Kumusta, Kabayan!
I have a USP9 full size myself, and i couldn't be happier. I just competed with it yesterday using lead bullets with very good results.
You just have to know who the most reliable reloader is in our parts. Their bullets left very minimal fouling after 100 rnds in 5 stages of IPSC conditions, with no failure to feed/eject and quite accurate. The fouling was also very easy to remove using lead cutter cpd and brass brush.
Of course, i had to prime the new barrel with 150 rnds of FMJ/JHP before i fed it with lead.
If you're somewhere in QC, contact True-Weight at Araneta Ave for quality (and cheap) reloads.
Regards,
New_comer
PS: As regards to preference, i went HK over SIG (my runner-up) simply because HK has a manual safety w/ decocker, SIG only has the decocker. But, it depends on you, really. Buy what you think is best for you. Another thing, SIG is much more expensive than HK. You could use your savings to buy a holster, mag pouch, a good gun belt, and lots of ammo. Stay safe, kabayan!