A cable slide will wear out your cables faster than a roller guide. I would think they would also impart more friction onto the cables, slightly decreasing the speed. Other than that, I'm thinking not all that much difference.
Don't sell yourself short, if you have the time & money to get any bow out there by all means go shoot them. The high priced ones cost that much for a reason. Don't get me wrong the lower end bows can kill just as well as the high priced ones but there is alot more technology that goes into the upper end making them in some cases more forgiving, faster, lighter, better draw cycles, more quality control, better strings, etc... Something to think about, how many people do you know that have shot a high end model in lines such as Mathews, Bowtech or Hoyt decided to go buy a new one after 5 years and went and bought a low or mid range bow? They always go back for that top model, if they can't afford it they usually wait til the next year. If your finances are keeping you in the mid range one bow I'd recommend you to try out is the Bowtech Assassin, you can get them as a package for $599
Only a guess on my part but I'm thinking it doesn't make much if any difference in shootability, etc. If it did, all the manufacturers would use one or the other. As far as cable wear, I'm in the process of changing strings on my Hoyt Trykon, 2006 manufactured w/original strings. The string has some fuzzies but the cables show no wear whatsoever through the sliders. Just keep all waxed.
Just took a look at Hoyts site. There higher end hunting bows all have rollers, then the slide is used on the others. So its a cost thing from that aspect. But then when you look at their 3d bows, they all have the sliders. So why wouldn;t a higher end 3d bow have a roller?
I'd search this topic on Archery Talk or post it, pretty sure you'll get a bunch of info.