Hello. I own an HKP7 and a SIG P210 and owned a Walter P88 in the past. Differences in action types is obvious, but all three are exceptionally accurate pistols.
IF the P88 is not as accurate as the P210, I think the difference would be exceptionally small. With loads they each like, these pistols are often capable of match gun type groups, not just once in a while, but consistently; I KNOW any of them can outshoot me.
The P88 has the thickest grip being a double stack, but I did not find it uncomfortable. The sights were "on" out of the box; not close, but "on."
With but one caveat, the P88 was reliable, but this is the reason I got rid of it. My gun would not chamber anything having a different bullet shape or ogive from FMJ or "ball" ammo. The bullet would get stuck in the rifling and lock up the gun. With stuff like Federal 115 gr JHP, Nyclad, or Remington 115 gr JHPs, it worked fine, but I handload quite a bit and wanted it to go with Sierra, Hornady, and Speer bullet handloads that didn't have to be loaded short for that particular pistol when compared to my other shot-a-lot 9mms.
This is the only P88 I ever owned so the information is not necessarily true for all P88 pistols, but it's the best I can do.
Best.