I was brought up using the Petzl Zoom, and currently have both a Petzl Myo 3, and a Petzl Tikka XP. Here are some thoughts:
The Petzl Zoom was great in it's day. It had a lousy beam, but it was very robust and reliable and helped countless climbers get safely around the hills at night. However, these days, there are certainly better options. I wouldn't get another one, and haven't used my old one for years, and probably will not ever do so again. I tried the halogen upgrade bulb in the Zoom. It seemed a tiny bit brighter, but only for a short while, before the alkaline battery just couldn't drive it properly.
The Petzl Myo 3 incandescent (same reflector as the Myolite you mention, but with a more powerful bulb) is a significant improvement over the Zoom. The beam is still quite poor in terms of rings, holes and artifacts, but the partial dimpling of the reflector do make it much better than the Zoom. However, I was a bit disappointed with the long-range usefulness of the xenon beam. The bulb isn't exactly bright for a 6-volt xenon bulb. When focussed tight, it can throw a bit further than the Tikka XP's boost mode, but by the time it has been focussed enough to do that, it is a very narrow beam. I find myself scanning around the countryside with the thin beam, trying to piece together the visual information. Frankly, in practical terms, the temporary boost mode of the Tikka XP is often just as useful as the slightly more penetrating beam of the Myo.
And since you are thinking about the less powerful Myolite, and you are intending to use NiMH (less voltage than alkaline), you will probably be even more disappointed than I was with my more powerful Myo 3. I expect the only real advantage of the Myolite over the Tikka XP might be in fog or mist, when the beam will cut through a bit better. But for that bonus, you will be sacrificing a lot of runtime. On the plus side, the function is great. The Myo series bezels are smaller and lighter than the Zoom, and the operation is easy, even when wearing gloves.
So one answer is: If you are choosing between the Petzl Zoom and the Petzl Myolite, I would go for the Myolite.
Another answer is: If you are wanting the Myolite to offer much better long-range route finding at night than your Tikka XP on boost mode, then I think you will be disappointed. If possible, I would try one out before you buy it, because I really don't think you will be impressed. Don't get me wrong - I think my Myo 3 is a really great hybrid headlamp and I like it a lot. It's just that the Tikka XP is also really great, and the incandescent beams of the Myo / Myolite range don't offer as much practical advantage over the XP as I was hoping for.