If I could, I would vote for both the P5 and P5C. As all the P99 are considered one serie, the other designs (P5, P88) should be treated the same.
I voted for the P5 as it is the only 9 mm Walther - except a P38 - that I own and shoot. When I compare to other modern pistols (SIG Sauer P225, CZ 75, Beretta 92 FS, Glock), the P5 is a superior design in terms of ergonomy (grip, multi-purpose lever, mag retainer...), shootabily (trigger, sights) and concealability. And it is so well made and designed!
Only problem: mine was not perfectly reliable at the beginning (some FTF when I closed the slide with the multi-purpose lever) but the more I shoot, the more the occurence is rare. Looks like things are smoothing.
Sure I would be excited to shoot a P 88 compact with the multi-purpose lever!
And I agree with Laurent, I have shoot in the vecinity 2000 rounds with my P-5C and when began shooting it, sometimes the first JHP on the magazine made my P-5C to jam so I put a FMJ first round on magazine and never have a failure to feed again.
Seem to be good reasons, but... There could be other options....like the P-5C, it is smaller, much more comfortable to carry all day long, it's accurate, reliable, it could be nice addition to your gun collection...
I do have a P5, just haven't gotten around to finding a holster for it. I would love to have a P5C, but given my current finances that is not an option. My next Walther is going to be a P99C for carry.