My experience with PEAK and REV2 say, that none really makes up for the other... I felt that even if PEAK did great pads, the REV2 analog oscillators just smear the tone in a more pleasing way, but only if that is what you are after... That is why comparing digital vs. Analog front end gets pretty hard sometimes because I felt the PEAK outperformed REV2 in many other territories... I really wanted both to be honest... I have to stop judging between the digital vs analog frontend, both stand their own right.
Even judging from analog to analog, or hybrid to hybrid you get differencies that boils down to just that... Being different, both having their own place.
Problem comes when you can only choose one of them... I would hate to choose between REV2 and PEAK... Between REV2 and P6/OB6 too because even if the raw tone of the two later would probably be considered "better" it again boils down to what you want from them... REV2 will kick their butt in both polyphony and engine depth anytime, while the two others will make even REV2 sound sterile... Also, if you absolutely want the most advanced Curtis chip synth ever created, I think REV2/Prophet 12 will fight in vain to claim that title... Probably for a veeeery long time now, as that chip has had its 15 minutes with Sequential/DSI, and I do not think we will see another poly curtis synth from them ever again. So if you ever wanted to have a curtis poly in your rig, now could not be a better time, and no... You will need them both because both Prophet12 and REV2 share 1st place I feel. For different reasons.
Compared to REV2, PEAK and SUMMIT will sound more defined, more strong in controlling the cardboard of your speakers... It sounds more pristine... So much it cannot relax, and smudge in a more oldschool analog way... You may not notice alone, but as soon as you start playing REV2 pads, strings and atmospheres, you hear the differencies emidiately.