A: As someone who has over 60 guitars,
B: I would never limit myself to one brand and the same is true for custom makers.
C: What I can say is that going to a custom builder will get you something that you can't get off the shelf and if you have some experience of playing and know what you want, then a custom guitar will really get you that extra that you are looking for.
A: I dont think my house has space for 60 guitars! Oh, I'd certainly TRY to get them in, but I wouldnt be able to move around!
B: This is a tricky. Custom stuff is by definition sight-unseen. You dont really know what youre going to get till its in your hands. Could be a Legra or Wez or Feline, could be an Ed Roman, or even Eric Devries. I'm gonna call it "Rhythm in Jump. Dancing Close to You" syndrome. You may not get quite what you planned for!
Without vast amounts of spare cash around a custom is a bit of a risk. Some of us are lucky enough to be able to afford to take chances with new builders, some cant. Plus, regardless of the financial outlay, we'd all love to try new builders with every giutar, but theres a matter of trust and knowing what youre going to get, both in quality and in how well it achieves what you set out to do with it.
For me getting my first custom was a decision that I very carefully went into, and I very carefully selected who would build it. I now know that I made good choices then, but I dont know that I'd make as good a choice with the second one. Perhaps yes, perhaps no. The only way I think you can know is to play one of their guitars, and by the nature of the beast, thats very hard to do (and even then, that doesnt mean that they're going to be able to achieve what you want with your particular guitar).
I have few biasses with produciton stuff - I just buy guitars I like. Its easy, cos you can try them out. Some manufacturers are...how shall we say, more likely to make a good guitar than others, but its possible, in theory at least, to get a good guitar from almost any of them. Because with custom you dont get to try them, I'm personally much more cautious.
C: Yep. Thats pretty much it - havent found what youre looking for in produciton stuff? Have a good idea of what you want and a good idea of what affects a guitars performance? Go custom.