The Twinlite is well-regarded for macro work but very dear. Canon recently brought in a new model, so the old model might be worth checking out used. (Often, when a new model comes along, second-hand prices for the old one drop quite a bit.) The differences between new and old aren't that significant, if I remember correctly.

The chief argument for buying a Canon-branded flash (430ex or any other) is that it will work seamlessly with any Canon camera. No compatibility glitches or gotchas. That has certainly been the case in my experience. However, I've never used a third-party flash, so maybe some of them are just as good and half the price. Someone who has used both will have to comment on that aspect.