These are my best times:
GPU
490 x 270 - 1min 02.7sec
245 x 135 - 1min 11sec
125 x 70 - 1min 45sec
980 x 540 - 1min 7.8sec
490 x 540 - 1min 1.69sec
980 x 270 - 1min 2.51sec
CPU
980 x 540 - 22min +
490 x 270 - 5min 40sec ish
245 x 135 - 7min 40sec ish
125 x 70 - 6min 35sec ish
My best time was rendering in GPU at twice as many tiles as GPU cores.
I am assuming that the Intel “update” made everything about 30% slower. lol