Depends on what you want to do with it. Are you planning on running a 166MHz bus (assuming it's an AMD machine)? If so, stick with the PC2700. Do you care if the RAM can be used with the next gen chips? If so, get at least PC3200. I'd get the PC3200 because very few people here will actually NEED more than a gig of RAM. In fact, there was one user on who said his machine slowed down due to having over a gig. I'd also get the PC3200 to run a faster memory/system bus and increase the bandwidth.
~THT