What's drawing you to santorini?
I've had a look online and most of the excursions on offer are matched by those in the Canary Islands.
If you aren't getting the spectacular views doesn't seem a fair trade off for almost half the holiday length but only you can make that judgement.
Somewhere like Lindos in Rhodes/Rodos Island has traditional whitewashed buildings and the old town and the island is comparatively cheaper.
All depends what you want from a holiday. If it is all inclusive all the way and chill out in the resort or excursions, sightseeing and eating out.