Note that these review centers are not ranked in order. There's no real quantitative way to rank them, as we've only asked the opinions of students.
MSA is one of the oldest in the review center industry and certainly has years of experience from which it can draw upon. Prices are on the expensive side, and the actual lectures are supposedly none too engaging, but in terms of quantity and quality of review material at least, this is the best choice for you. After all, they do supply most, if not practically all, the review books on the UPCAT and ACET you find in shops like National Bookstore.
Brain Train has one of the more aggressive marketing strategies among review centers, but it does have the history to back it up, having produced not only passers, but merit scholars from among its ranks. Their price is fair enough, and the review strategies are characterised as intensive–which is probably why they call it "Brain Train"–so this should be a good, balanced choice for students.
Another review center on the more expensive side, Ahead is arguably the second most prominent review center in the Philippines, next to MSA, and for good reason. Their review material is relevant and engaging, while their lectures have their uses, which is saying much as the same does not apply to many other review centers with ill-prepared lecturers. This is a solid choice, even for the money.
MentorsPlus is the cheapest of the four, and while comments from students have not always been glowing with praise, for the price, MentorsPlus seems to be a great deal, combining decent review material, with decent lectures. It's not a top drawer review center to be sure, but if you're a bit strapped for cash and want an affordable review center that isn't a complete waste of your time, MentorsPlus fits the bill.
-And of course, a shameless shoutout for this CollegeRev too: If you don't want to spend a single peso on an UPCAT/ACET review center, we do have review material you can access for free! Check out our UPCAT and ACET Practice Tests!