Which of the BikesDirect SS bikes has the best fender mounting options? Does anyone have any real life experience with ease of mounting or how effective they work?

Uno has eyelets and clearance, probably your best bet

Not to mention center pull cantilevers, for extra clearance. Here is mine running 35mm Innova studded tires with plenty of room for fenders.

Just use P-clips or Raceblades.

P-clips if you don't have eyelets. Yes.

I've used Raceblades before, and I hate them. They rattle like a pop can full of marbles, and no matter how well I got them adjusted, one good pothole and they'd be rubbing the tire.

Maybe your rubber mounts aren't tight enough? I have a heavy 40c version from Planet Bike and it's just fine and stable, even hopping curbs, etc.

Starting with fender eyelets and adequate clearance is a really good idea if you want to run full fenders, which do make a big difference. If you're considering doing your own build, the Jury frameset from BikeIsland (same folks as BD) is well suited to fenders, though the cantis on the UNO are a big plus.

The Fantom Cross UNO is geared substantially lower than the other FG/SS from Bikes Direct (38x16 instead of 48x16), so take that into consideration unless you're ok with buying a new crankset or 13t/14t cog if you want to gear it higher for street riding.

You mean swap the chainring, not the crankset, yes? Swapping cogs is obviously a lot cheaper (and easier) in any event.

A new chainring or cog will fix this, no need for whole new crankset.

Yeah go for the full wrap fender. Raceblades work wonderfully compared to using nothing at all but compared to full wrap fenders they suck.