Are you overclocking?
If not, go for the tight timings without any doubt. The stuff rated at a high speed will run at 200MHz anyway just with looser timings
If you are overclocking then the whole debate of timings vs speed comes in
Basically there's not much in it at all as running a divider on an A64 doesn't really hurt performance like it would for the traditional FSB architecture, such as an Intel P4 or an Athlon XP
The general consensus is that tighter timings are better