I have a Twitch II and a Flash II with Zytel handle and am satisfied with both. The Flash with aluminum handles is more expensive, but looks really nice.
If you are choosing between the Flash I with aluminum handles and the Twitch II, I think the recipient will be happy with either. I haven't handled a Flash I, but the index finger "flipper" on the Twitch II makes handling this small knife very easy.
My impression is that the Twitch I, Twitch II, and Twitch XL were all designed to be a small knife, whereas the Flash I seems like a miniaturized larger knife. Even so, the Flash I with aluminum handles is a very cool looking knife and one that Id be happy to have.
All I can tell you with certainty is that I have a Twitch II and I use it a lot. For a small knife it has quite a bit of cutting length as none of the blade is wasted. The flipper works well to protect your fingers from slipping and the A/O mechanism has worked well so far.