The HyperX is considered pretty good, and it's a lot cheaper (compare prices on the "dual pack" and just 2 individual modules, there is no difference other than a guarantee that the two modules work together in a certain board they tested with). They're both rated for similar timings and speeds, and I believe they use the same chips as well (Winbond).
If you're going to be overclocking a 266MHz processor to 333MHz, then PC2700 modules should be all you need. Even if you manage to go a bit higher than 333MHz, the timings shouldn't need to be reduced unless you go up to like 350MHz or higher. A single module of HyperX PC2700 256MB is 47 bucks, while PC3200 is 60. Even at 400MHz, the PC2700 should run at 2-3-3-6, maybe 2.5-3-3-8. Or you can go inbetween and get the DDR370 modules for 54, which would give you a bit more headroom.
There's not a whole ton of reason to get Corsair unless you really wanted to get a high overclock, and that's only because they have a longer period of reputation for stability.