You can buy alcohol for home( hotel balcony) consumption at Government outlets which are not very widespread.Cheaper than airport duty free but dearer than Goa.Drink at restaurants no problem except the 1st day of every month when you can only buy in hotels.
Food is very different to Goa. Goan Indian food is pretty similar to the food you get in Britain, Kerala Indian is somehow tastier, more coconut based ( they fry in coconut oil) but not like the Korma style coconut based meals you get here. We were dissappointed with the lack of local originality in Goa.You might find less choice of non Indian food in Kerela.
To really appreciate the differences in the two states you must get out and about. Kerela's real advantage is the hinterland.Fabulous variety of scenery and wildlife.
One disadvantage of Kerela is the fact that First Choice( the best package deal operator in my opinion) only offer 2 week holidays based from Gatwick.To Goa you have options on three weeks from three airports.
The other consideration is the general "feel" of the place. Depending on your taste , the northern Goan beaches can be extremely "tacky" in my opinion.
Interestingly, we never had a single stomache upset in Kerela, everyone seemed to be suffering in Goa !!!