Six of one, half a dozen of the other, IME. They both present certain challenges, but if you have a little experiencing modding stock pedals successfully, you can do it.
The real question is what kind of sound you are after. Those two units produce different effects. The 808 is well-known, and it's a very good version of what it's supposed to be. The Tri-Boost I tried a couple of years ago, but didn't like the linear power boost at all and the tuning of the germanium diode for the treble booster was a little trebly, so I redesigned the circuit and built my own the way I'd like it. The clean boost was just fine.
Ultimately, I don't really care for having the treble booster and the clean boost in the same unit if I can't use them together. If you've only got one pedal in your rig, then the versatility of choosing which kind of boost you want is nice I guess, but you can't really change between them in the middle of a song like you could if you had independent stomp switches for each type of boost. I prefer the versatility of either having both of them on foot switches or having completely separate pedals for each type of boost.
Whichever pedal you decide to go with, the build quality is good if you're good with a soldering iron, and the sound quality is first-rate. They put out good circuits. Whether you're simply wanting boutique quality at stock prices or you're building your skills so that you can ultimately build your own pedals from scratch with your own designs, BYOC is a great way to go. I've heard the people are also very informative and supportive in case you have any questions.
