Good review, yeamac. You've pointed out a lot of things that are worth a close, hard look for those considering similar flashlights as headlights.
Even though I think a few of the evaluation comments you've made need to be examined a bit more carefully from a few more angles, you did a nice job in terms of a quick review.
In terms of bang for the buck, the Ultrafires seem to offer a lot at a great price.
I'm tempted to buy at least one of the Ultrafires just to have it. I love the fact that you can run it with a 1xAA body or a 2xAA body (did yours come with both tubes?).
If I were you I'd pick up one more 3-pack of lockblocks, strap them all (Fenixes and Ultrafires alike) to bike and helmet and cut loose, bike ablaze. That'd throw a little light to see by.
Depending on your ultimate decisions on what to keep, you might experiment with some combinations in the mean time. For instance, try strapping two Fenixes to the handlebar and one Ultrafire to the helmet. If the handlebar lights run low, the helmet will get you home. Playing around with both in real night-riding use might actually be fun, at least as an experiment.
On the rechargeable batteries and capacities, not all seem to be equal, even if rated with the same mAh capacities. I think the general consensus is that the less well known (and less well evaluated) the battery, the less consistent or reliable the rating might be. I've got the sneaking suspicion that the batteries you bought in bulk might not be up to the same level as some others (like the Duracells that were mentioned). I say this mostly based on the limited run time you are getting with the Fenix lights with those batteries, which seems to be an awfully short run time. If you buy some of those Duracells for testing, watch out for pricing. They seem to go at regular price for a whopping $15-$16 for a set of four. A while back, I saw the same 4-packs on sale at a local grocery store for about $8, so watch for them and you might run across some on sale. I think it would be worthwhile for you to test some, and the money would not be wasted since you essentially just investing in a few more good rechargeable batteries you'll be able to use for a long time.
On the battery fit comments, it's true that you'll run across that now and again. Not all batteries from all makers are the same diameter, and some have too large a diameter to fit inside certain tubes. I can't remember which ones they were, but some time ago I put some AA batteries into one of my L2Ds and had a heck of a time removing them because of the diameter.
On light tint, you do have to watch out for the perception associated with tint. We tend to perceive those lights that seemingly project with a whiter or more bluish tint to be brighter, and I'm pretty sure that's more to do with our own mind's preconceived notions about what is bright and what is dim. Anything that tends to run to a warmer or more yellowish tint seems to be deemed by the brain as not being as bright, even when that's not really the case. And we all seem to have our preferred tints. I've heard comments from others who seem to like the more yellow tints as seemingly easier for them to see with at night. I tend to prefer the whiter seeming lights, though.
On light output and lumens, etc., I'd probably never try to guess at lumens by just using what my eyes tell me. For actuals on that sort of thing, I think it needs to be measured a bit more scientifically (that is, with equipment made to take such measurements). Anyone seen any test test results showing actual output for this particular incarnation of the Ultrafire C3 Q5? On the CandlePower Forums, perhaps?
Overall, I'm pretty impressed by what I've seen of the Ultrafires. Too bad that whoever makes them doesn't have more of a visible presence. I'd guess they kind of have to be looked at as a "generic" or something. I've done a little bit of reading to try and find out more about them (who makes them, where they come from) and I have to admit they seem to be what I'd call a knockoff style of light (I think that would be accurate). Lower cost, very effective, but you get what you get. Good performance, but I'd have to guess lacking in certain quality and quality control categories on levels that might not be visible just by looking at them but that could be important in terms of longer-term performance and durability. Probably a bit sketchy if you need customer support or replacement (perhaps). I see the name "Ultrafire" as a pretty blatant attempt at tapping into people's name brand recognition for "Surefire." Just my take on that.
Again, yeamac, I think you're doing a good job with your initial evaluation. You're obviously catching a slight bit of flack, but you're adjusting to the criticism and responding reasonably. Keep up the study and keep posting thoughts and results. You're obviously giving it a conscientious effort and this discussion should benefit all interested parties, I think.