Seeing as I own both, I feel qualified to answer. First, let me say that I am not a fan of, nor do I own anything chambered for the 10mm Kurtz. My P99 is in the tried, and true 9mm!!! The G30 is a great pistol, BTW, and I do carry it when I feel the need for a hand cannon!! I carry the P99. This is my second one, having sold my first one in a stupid fit of anger years ago. I carried it then too. IMHO, it is the most concealable full size service auto in the world. In the intervening years, I have tried almost every pistol that you could think of from Berettas to Taurui. I came back to the Walther.
It is a more accurate gun than my middle aged, bi-focaled eyes will allow, but I do alright. The recoil is quite tame, and I like the adjustable grips. Standard capacity 16rd mags are EXPENSIVE
. When they can be found at all. Mine came with two, as standard equipment!!!
My advice is not to abandon your G30, but augment it with the P99!!! God, I hate to do this, but if you MUST deface yourself, and shoot the 10mm Kurtz, (I am loath to even speak it's vile name) then the Walther is the way to go. At least you will have a "gut Deutsche waffe"!!!!! Now, go do the right thing, and buy that Walther!!!!