Well this is an interesting challenge - I've been pondering it all night in fact. The issue is how you define best quality ... and I think the OP is asking for the best quality balancing all relevant factors.
Still I have distinct favorites in particular areas and my thoughts are also informed by my use of my single CR123 lights as EDC lights - and I work in a business dress setting which leads to certain preferences... My favorite UI is the HDS interface - I still EDC my old Novatac 120P - it is modded with a K2 TFFC and the output is about the same as the current HDS lights - it has a PEU trit bezel and still works great so I've had little incentive to upgrade to a current clicky which doesn't bring anything significant to the table and given that I thought the Novatac was pushing the envelope for a reasonable pocket EDC light the bigger and heavier current models are heading in the wrong direction. I understand Henry's philosophy on robustness - but I'd trade a bit of bombproofness for a smaller form factor with similar build quality (not robustness but fit/finish) and the same UI...
While the Novatac has never failed me - if I were pushed to have only one light and had to count on it to work all the time - the more complicated Novatac/HDS setup may not be my first choice - the electronic switch, etc... would give me pause - I'd probably opt for my Surefire E1L. It just works, has two modes but is otherwise a pretty simple light. Surefire build quality - nearly as bombproof as the HDS lights (the bezel being aluminum being perhaps a weak point albeit a small one).
I have a Sunwayman V10r ti+ - neat light but I admit that the titanium body is what I like the most. The control ring, for me at least, is a neat but in actual use somewhat uncessary feature - I find myself at either low/high or some low/mid level pretty much anytime I use it and rarely am I making small adjustments to how much light I need. 2-3-4 levels works fine - arguably 3/4 being ideal given the upper end of modern emitters. But that titanium body... the heat transfer, the feel... I have several titanium framelock knives that are my primary daily users, my watch is titanium as are my glasses. I clearly dig the qualities of this material and think it is pretty close to ideal for an EDC...
If I have a problem customer service matters - Surefire and HDS are known for their excellent service and I've availed myself of Surefire's with great results. I don't know about Sunwayman - Novatac was helpful when I needed them but that was admittedly back when Novatac was HDS - not sure these days who is running the show - and one of my favorite EDC lights is an Arc6 which as we know is a true orphan these days...
I also like using RCR123's which is fine for most but is a knock on my Surefire lights such as it is.
This leads to a bit of a quandry - but in the balance if I had to pick one and price was not a factor - I'd probably say that the McGizmo Haiku is the single best quality hands down 1xCR123 based light. I would consider one of Mac's custom titanium lights a close second. I'd say the more aggressive driver setup and the fact that they are for all practical purposes unavailable to be somewhat of a disincentive. I do like the basic styling of the Ti-Tri EDC a lot. I also like that there are some driver options that give you four levels and the possibility of a real low low.
Anyway - here is what the Haiku does well - which is most everything. It strikes a balance from a UI and driver perspective of giving you reasonable light with a gorgeous beam for a reasonable period of time. It is meticulously well crafted and backed up by a maker who while a custom builder has the track record and the inventory to meaningfully service the light. All the parts are well tested, proven and demonstrated in the field to perform reliably every time you go 'click'. The titanium body is a work of art but a robust and reliable work of art. It is, in short, a very well thought out light that meets 3-4 standard deviations from the mean every need you might have for a light. It won't light up a field for a couple minutes on high - it does not have the most cutting edge UI. The UI is a reasonable one that is easy to understand and like so much about it - meets the needs of most if not the absolute ideal.
For me personally it has two issues - one is price which is what it is - the second is the absence of a really low low which I use a lot in my EDC lights. The nature of the platform is such that I suspect there is someone out there who'd program a 4 level light engine for it however so at least one issue may be gotten around.
I love the 1xCR123 form factor (have between lights and headlamps 8-9 of them and have owned a raft of them - and one day perhaps next bonus time I will have a Haiku.
