I would wait for the GRX Di2! I am building up a bike with it and that is the main reason I didn't go w/ Salsa bcs of only their pre-builts. The Ti frame should outlast you. With exception of my MTBike - all I ride is Di2. If you want another opinion...Gravel Cyclist did a long term ride and comparison of the Di2.
In regard to cost - buy what you truly want - don't settle. I waited for my ideal build - I will be happier for the wait and in the long run. Just my 2 cents!
I recently went through this same dilemma after ordering my GR300 from Lynskey. I ordered on 3/9/20, so basically right before the effects of COVID on the bike industry became visible. I had been shopping for a Warbird for several months, but found a bigger than usual discount on new Lynskeys, so decided to go that route with a GRX600 build. Delivery took 12 weeks instead of 4, but I’m glad I waited.
One question, if you’re considering a mechanical GRX groupset on the Warbird, why not consider the same on the Lynskey? If the Di2 is the holdup at the moment, but they could finish your build with GRX600 or GRX800, maybe that would be a reasonable compromise to get your bike sooner? With that being said, I’d actually be surprised if they could get the mechanical GRX any sooner than the Di2 version.
Best of luck in whichever direction you decide to go, I don’t think you could go wrong with either bike.
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