If you want to set and forget, buy Shimano. You get Shimano reliability, ample support and spare parts availability. My buddy bought a used Ultegra Di2 groupset, accidentally bricked his RD during a firmware upgrade and Shimano still sent him a replacement part no questions asked. Also for US customers, the tariffs have lessened Ltwoo's value, so I'd definitely lean towards Di2 if found for a good price.
If you like to tinker and experiment, LTwoo has been great for me. Plus you can do hybrid setups like Shimano chainrings and XDR cassettes and fine tune the shifting to be exact. I also like the battery flexibility of using 14500 batteries. If you go LTwoo, I'd wait for the new V4 groupsets that will come with the upgraded 100g flat mount calipers. Only issue is that you won't get much direct after sales support (only so-so vendor support), so I'd at least stock up on spare components if possible.