IME 'ration balancers', just like anything else, feed or otherwise, can be good or bad, &/or suitable for your horse & his situation or not. I do think, after analysing a fair few, you generally tend to get what you pay for with them - eg. the cheaper ones may have lots of crap, not be so well balanced, you may need to feed a whole lot more of it, etc.
I would generally avoid feeding anything with grain &/or molasses to horses, of which many of these contain, and as for which ones may be appropriate for your situation, it depends on what your horse is already getting from his diet, so at least a basic diet analysis is a good idea IMO. I personally subscribe to a great service called FeedXL.com that I reckon are great for that sort of thing & also have equine nutritionists(independent of feed co's) to ask questions of & get help from.