Try the Menzerna IP just once and you will see for yourself - it finishes equally well as 2.5 and is stronger IMO. I have both, but will not be buying any more 2.5 after using IP. As far as cut, put some of each of the products on a pad and rub it into the paint by hand and listen to the "grit"...IP has more abrasives than 2.5, yet you will find that they finish down equally well (acutally, I like the finish of IP better too). Per ounce, price is comparable too.
Everybody has their favorites...but I think you will like ALL of Mernzerna's abrasive prodcuts.
BTW, if you plan on (or are willing to) perform a 2-step process, use Menzerna Power Gloss followed by FPII (or any other light polish). PG dusts quite a bit, but is absolutely amazing in regards to how well it finishes down considering it cuts heavily. Just last night I did a black SUV that was JACKED up so I knew I would be performing a 2 or 3 step polish process. Under 2 1000 watts lights I tested Optimum Hyper Compound, PB 3, and PG head to head using a rotary and a medium polishing pad. Both PG and PB 3 cut better than Hyper, but PG finished down better (less rotary holagroms) than PB 3, making PG the clear winner. I was able to remove most heavy swirls and scratchs and yet the holagrams were light enough that I was able to follow with #9 and a finishing pad and be done - 2 steps where normally 3 would be required - I'll pay extra for that

Also, though Hyper Compound does not cut as heavy as claimed, this will be by go-to compound for medium defect removal because it is very easy to use, does not dust, finished down very well, wipes off easy, and it's relatively cheap.