If you can find any hotel reviews on the two properties I would read those first as if one has great reviews and the other dire reviews that might make the choice for you.

Just my opinion but I would imagine the weather would be more settled in Lanzarote in October, whereas in Turkey you could be either lucky or unlucky if you know what I mean. Lanza is also an all year round resort. With Turkey the Med coast (Side, Belek etc) is all year round, but the Turquoise coast (Marmaris, Olu D) and Aegean Coast (Bodrum etc) are seasonal.

Doe