Hi Josh.
I'm certainly not an expert like Gary or Jim. I've only owned and extensively used one machine. I've had a good experience with Camaster - reliable machine, well built, capable - even though I have one of their lower end machines. The folks that work there are nice and knowledgeable and the forum is excellent. Recently went the path of requesting a quote for a much more expensive machine and it was a bit hard to get anyone to engage, call back, respond to emails. Probably all very busy but it wasn't the most satisfying experience. On the other hand, the Shop Sabre people were extremely welcoming and responsive - knocking out multiple quotes, providing a lot more information, etc. I had been cautioned that they would be "giving me the hard sell" but honestly it was a very positive experience and the way I wanted to be treated by a company I may be sending 20 -40k.
My sense was that Shop Sabre started at a somewhat higher point in the market and was open to more customization - for example, I could spec an ATC on any of their machines whereas the Stingers can only be gotten with manual spindles. There seem to be a lot more options on the Shop Sabre or perhaps they are just better at making it clear what can be optioned. They also don't seem to be as opposed to in the field upgrades - my experience with Camaster on that idea has been basically its a no go. They referred me to a third party CNC upgrade company that wouldn't return my calls. The videos Shop Sabre makes are quite informative (they have a more savy marketing approach, I guess) - something Camaster doesn't seem to do much. They have a forum but it is some sort of facebook group that requires ownership so I can't say whether it holds up to the excellent Camaster forum. Most likely can't go wrong with either company although I only have personal experience of ownership with a Camaster. I am, however, about to put a deposit down on a Shop Sabre as an upgrade given the excellent sales experience I just had.
I assume for 26K you are looking at a Shop Sabre RC8 with a manual spindle? I still think that for a machine of that price the additional 4K for the vacuum setup is well worth it. It seems to me that you are really exploring a much different class of machine when you compare a 4x8 Stinger III or RC8 against a bolt together Avid system. Whether you need all the extra rigidity and capability is up to you. My feeling was that I had no intention of ever having to upgrade again so I wanted something well beyond my anticipated future needs.
Good luck with the quest.