My experience may be a bit unusual, but I have no complaints about the stock Intel 2200BG card. My Linksys WRT54G(L/4.0) router is only operating at 25% power to the antennas and the sentia displays full signal throughout the small house (~1000sq ft) I live in, and a decently strong signal on the back deck through the asbestos siding. At my girlfriend's place, I can pick up three unsecured wireless networks with the Sentia. None of these were even displayed on her notebook with either a USB external antenna and PCMCIA card.
I don't really know how to compare the Intel card beyond that. It works great here in the office, but then the wireless coverage at the University is excellent anyway. So, I guess for my situation I really don't have need for any more than what it provides.