Have an example of both and like them quite a bit.
The P5 is particularly well-suited for leftys. The only beef I had with it was that the trigger was a bit crunchy at first. This is due to the fact that the firing pin "falls" out of line with the hammer and has to be lifted by the trigger action on firing. A bit of cleaning and polishing took care of that. It was remarkably accurate right out of the box. Spare mags run about $35 and can be obtained from any MecGar dealer (MecGar is now the maker for all Walther factory mags, and they are making the "legacy" mags as well).
Custom wood grips are available from Earl's Service but, at $165, they won't be in my safe any time soon. But they sure are handsome.
The P88 Compact is wonderful little handgun, I'm surprised it never caught on. I've always thought it was a HighPower slide on a Walther frame. The trigger mechanism strongly resembles the early PPK mechanism and can be polished and tuned by a good PPK smith. It comes with a trigger overtravel stop you adjust with an Allen wrench. I thought my trigger was vague out of the box, but a little polishing with India stones, plus some TetraGun grease, took care of it.
Curiously, it seems to have gotten more accurate the more I shoot it. Clintonista mags run about $35 from places like CDNN and Earl's, you can find hi-caps at One Eyed Jack's, KY Imports and Earls, they run about $100-$125. Occasionally you see them on gunsamerica.com for a bit less.
PWL makes some nice leather for both guns.
Both are fine choices, either as home defense or CCW.
Pick the one that fits your hand the best.
Ken Strayhorn
Hillsborough NC