I have found that all three of my mitts (Aldi,
Altura, no-name market stall pecials) have a seam that runs between my thumb and forefinger, leaving a blister on the webbing after about half an hour of technical stuff. I got a freebie pair of thin full-fingered gloves by Kona, and whaddaya know? No seam, no blisters. Cubesters 661 gloves are the same... thin, light, no blisters.
So, long distance, not much gear-changing or wrestling the bars, fingerless,
technical, lots of gear changing and wrestling, full fingered Kona freebie thingies.