I've heard mixed on 25 vs 35. Pros to 35 is that it very standard on high torque applications such as arms and drivebases and since it is larger, it is easier to work on which comes in handy if you blow a chain the finals. 25 is smaller and lighter but it is a pain to work with in a timely manner with how small the master links are. Great for small applications such as rollers, set and forget.
I have heard of a few teams using a combo in their drivebases to save weight. Use 35 chain to drive the the middle set of wheels in a 6wd and have 25 spanning to the front and back. So even if you blow a 25 chain you can still drive your main dropped center wheel. To save such a small amount of weight I'd rather just drill a few holes but if your aim is to use as little weight as possible from the start of the design it isn't a bad idea.
For me, 35 as much as possible. Less spare parts to plan ahead for and I know when properly tensioned it will be consistent and an easy fix if something goes south.
Pre-season purchase? Kinects!
