I've only ever visited Hydra and Spetse and Poros on day trips so don't really know much about the islands. I do visit the Peloponnese area of Southern Mainland Greece regular so I will try and answer some of your questions.

Is mainland Greece much more built up and busy? I haven't found any problems. When travelling around there are some very small villages (it is useful to be able to speak some Greek ) that probably haven't changed much over the years.

Is it more modern and has less of its culture? In the Peloponnese there is a wealth of culture and history. You have the birthplace of the Olympic games - Olympia. The first capital of free Greece (before Athens) - Napflion. There are many ancient sites, some in better condition than others, such as Mycenae, Corinth, Mystras, Sparta, Tripoli, Argos to name a few. The amphitheatre at Epidaurus still puts on plays in July & August.
In the Northern part of the Peloponnes there is a ski resort, Kalavryta where you can get a rack and pinion train to the coastal town of Diakofto ( I don't like Diakofto very much but the journey there and back to Kalavryta is worth it). The views are amazing but you need to get a first class ticket and sit with the driver for the best views.
I could go on for ages but I don't want to get boring!

Are the beaches fewer ? different? more crowded ?
Is it less like a holiday resort and more like a working town/city ?
It depends where you go. At peak times, in some of the popular resorts, the beaches can get very busy because the Greeks go there for holiday's and weekends. Some of the resorts are still working villages and aren't yet totally geared up to tourism but that's what makes them special.
Has the mainland lost a lot of its original features to modernisation?
Some areas have but thankfully not all.
Are there more wines to choose from?
Can't really comment too much on wines but there is a very nice wine to be got from Nemea.

Can't comment on these questions.
Is the food different? more varied?
Is it cheaper/dearer?
Is the weather different?

Thanks for that, its a pretty good start :-)

i've only stayed on the mainland once and found it to be almost the same as the islands i've stayed on. i've mainly stayed on small islands in june and food and drink were cheap depending on what type of place you eat at. trendy spots tend to be expensive and off the beaten track resorts cheaper in my experience. we stayed in stoupa in july 2003 prices for a beer 1.50 euro average and meal for 4 around 35 euro's. 2 adults 2 children, children did'nt eat large meals but saying that they don't do kid portions so charged the same.
stayed in angistri last june and on average for 4 adults 50 to 60 euro's a meal including drinks. the most we ever paid was 90 euro's but that was for a birthday bash nothing barred.
paul

Hi in reply to Islands versus Mainland.

We much prefer the Mainland.

We went to Corfu, not far from Sidari infact Roda, just along the Coast. Nice relaxing holiday, but too British for us. We found some of the Greek food adapted to suit English Taste, but we did find a couple of lovely restaurant that did good Greek food in Roda. If you went and bought your own food it was good, the Bakeries were typical Greek.

We went to Marathon Coast, Mainland, definitely Greek, my Husband is Greek, food lovely, very Greek. Prices very reasonable, pre Euro though.

The whole feeling of the Mainland is different for us, we love it, it's the real Greece.

We are off to the Tolo in the Peloponnese in a month, and cannot wait.

I feel the actual Holiday is a little more expensive, and there are less Deals to the Mainland, but that will change, as more Holiday are being offered, the extra is well worth it we feel.

The price of Food is think is very much the same, everything has gone up so much since the Introduction of the Euro, but that seems to be Universal for Islands as well as Mainland.

The beaches seems the same, you have good and not so good, but on the whole good.

All in all the the Mainland seems to have the History, the atmosphere, the food. As a previous writer said, for History the Mainland wins Hands Down.

We will try more of the Islands, just to make sure we are not missing anthing, but so far the only Island we would return to over the Mainland is Kefalonia.

It is so peaceful, so nice.

I think it comes down to what you like, some people only like the Islands, try the Mainland if you love it you are hooked, I cannot explain the difference in the feeling of the Mainland for us.

When in Corfu we went on a Boat trip and stoped briefly on the Mainland and the feeling was like, phew we are home.

My Husbands, Families, I must say, both sides are from the Islands, but now a lot when returning back to Greece after living and working abroad, live on the Mainland.

I think it is entirely personal.

Whichever you pick though, it is still Greece and in my mind you cannot loose.

Love Greece.

I've visited a few islands and loved them but last year my wife and I visited the Pelion region of the mainland. (Near Skiathos). We stayed for two weeks in Lafkos in the hills to the south of the region.

it is absolutely gorgeous. Very picturesque, quiet, unspoilt and not too may tourists.

So in conclusion it's not easy to seperate the two. I love Crete and will continue to go back but Pelion would be next on my ideal list.

We've been to lots of Greek islands but have also been to the mainland 3 times - Parga, Stoupa and have just returned from our first visit to Gialova in Messinia (Peloponnese). The mainland places we've been to feel very much like islands, all have glorious beaches, fantastic scenery and friendly locals. The food is pretty much the same though you always get variations wherever you go.
Parga is one of the most beautiful towns in Greece, very cosmopolitan with many nationalities visiting. The drive up to it from Preveza is stunning and the roads although huge in comparison to little island roads are so quiet! There are many fantastic beaches to be found and the scenery if you go up in to the mountains is gorgeous. This was the only place we have ever seen a tortoise!

We absolutely loved Gialova it's a very quiet little village - it used to be one of the main wine producing regions but that has all closed down now. Lots of accommodation scattered around in the hills and very popular with the camper van brigade. Fantastic beaches surround it including Voidikilia one of the best beaches in Greece! Because it doesn't feature in any mainstream brochures there are hardly any Brits there so everything is still very Greek, all very laid back! Nothing is geared towards Brit tourists and you will not find any British food on the menus in the tavernas!
The tavernas have a very varied menu and it was no more expensive to eat out there then anywhere else we have been. In fact probably cheaper!
We had lots of archaeological sites close to us - all protected so no building allowed near them and a huge lagoon area where we saw terrapins and we were also lucky enough to see the rare African Chameleon - it's the only place they can be found in Europe!
We also drove up to Olympia which was 2 hours away but well worth it.

To us being on the mainland is no different to being on an island - unless you choose to go to a big city where of course you will notice differences!

As you've been to Sidari which in my opinion is an extremely built up touristy area of Corfu you'd be bound to notice a difference if you go anywhere that doesn't feature in as many British brochures!!