I was debating these two bikes as well for the same reasons. What did you end up going with?
As a Mach 429c owner, I recommend 1. DW link great for climbing, but still provides a little cushion going uphill
2. Head tube angle slightly relaxed for balanced up/downhill performance. If you climb steep hills this helps a lot. I hate fighting slack geometry on a steep climb!
3. Acceptably light weight. This carbon frame isn't as light as the newer SL model, but I was able to build a large size to just over 25lb(Roval Traverse SL wheelset helped here!)