Hi we have been to both resorts and of the two we preferred Torrie as we felt there was more to do and at night the whole area from the front all the way to San Miguel where the shops, bars etc are came alive. We liked the Marina in Benalmadena but felt once you had been around it a couple of times that was enough so really one visit during the day and then another in the evening is sufficient. The train service is really good and easy to get to in Torrie and from there you can visit quite a few places very easily and cheaply. We stayed at the hotel Sol Do Pedro in Torrie which is part of a 3 hotel group with plenty to do and very nice surroundings. In Benalmadena we stayed at the hotel Bali and although anice hotel we felt it was more suited to families and as a couple we felt overwhelmed by the amount of children running around ALL night!
Good luck on your choice and I am sure whichever resort you eventually decide on you will have a great holiday!
Cheers!
Tony