The PVC drums can warp but are you really going to ride it in the sun? If they are round now, they're probably ok. The aluminum rollers are better and should last longer. The belt can be replaced for probably not too much money.

Rollers are more pleasurable to ride IMO than a trainer. The resistance you'll get will come from the gearing on your bike and will have more of a real world road feel versus the trainer. You'll have to keep you attention focused because you can ride off of the platform if you are not careful (just like on a road) which adds to the enjoyment of a workout. The rollers will get your heart rate very high if you choose to but you won't quite get the muscle workout a trainer will afford. Hope this helps.