Definetley go with slides, I think the slides that you are relating to are the Lippert Schwintech slides. I may not have spelled that correctly. They have two tracks and motors on each side of the slide. I would expect this design is a lot less cost to the manufacture as there is not a lot of parts, steel underneath or hydraulics.
There is quite a bit of info on these and a few youtube videos. I suggest you look at them, it may calm your fears and load you with questions to ask when look at RVs.
I read that one of the main issues on the Schwintech is you must continue to hold the switch down for 20 seconds or so after the slide is out in order for the motors to sync. People that had the old style slides and are used to releasing the switch just when the slide is out and carry that habit with them causing issues. I also read a few threads with motors burning up and dealer replaces with the same motor and it burns up again. I suspect this is not a schwintech issue but the manufacture not specing out the correct size motor for the weight of the slide. Just research it and go loaded with information and questions.