pci cards are a fraction faster than usb cards but they would'nt sale usb if bad performance. The past year differences became very minor between the 2 systems.What's more important is to adjust your pc for audio and midi recording and to have the perfect settings.We should know about your setup, OS, processor ram amount, intel or amd etc............too be able replying correctly.
One wrong setting and problems guaranteed.
A few tips; the soundcard driver should be compatible with the motherboard's chipset, use your pc only for recording and music, use XP as OS cause it will not tolerate a wrong setting and stability is ok.
Recording software; cubase sx or nuendo is quite good for audio editing and they have a powerfull audio engine.