For the past 10+ years I've built my systems using Asus boards (after a horrible experience with MSI a long time ago).
During that time - I've built one GB system for a friend - and that board recently took a nose dive with the bios being corrupted (couldn't get it to POST at all.. - even after re-flash, etc.). This was after 3.5+ years (4790k) and a relatively inexpensive (mid-range) board.
Recently - my main rig (7700k / Asus Maximus IX Code) also had posting/stability issues - wherein I could get the system to boot, but the system would completely hang after ~10-15 minutes uptime. This was after only 2.5 years being built - with custom water loop, etc.
I also have a secondary/backup system with an MSI mATX board (b350m Mortar Arctic).
Getting to your question - As others have noted - the Master, CH8, Ace are all effectively on the same "level" from a general price perspective. Even Buildzoid notes in one of his vids that of these three - you really can't go wrong with any of them and to choose the one that best fits your individual needs.
IMHO - The difference (that made me switch back to the GB Master) comes down to advanced components being introduced (in some cases - across all of these boards).
Specifically for the Master - the VRM Coolers, the 12+2 phases (with new Infineon controller chip(s)), etc. I've also heard/read several times during the various reviews online that these GB boards are also "closest to spec" with respect to supporting these new CPUs/chipset requirements.
It also easily OC's my RAM without much trouble - assuming you put the work into it (running 2x16GB Ballistix Sports ATM on a very stable 3400/15 and I've gotten the speed up to 3800 with a quick OC test).. At this point I'm waiting for additional bios updates to come in to address some of the latest noted issues (not board related).
All said - I've been running this board since launch - it certainly has it's quirks (they all do) - but the quick turnaround in support for the fan curve issues, as well as the continued updates by Matthew and this forum add to the overall value.
The overall build quality of this board is certainly very good (better than my Asus IX Code actually).
I'm happy with my purchase and (knock on wood) hope that this will end up being a solid board for years to come... Certainly recommended..