I play both an i15, and a G15. I hit a draw , so the i15 doesn't hurt me too much, it will hurt me if I don't turn it over and resulting long pushes, but doesn't seem any worse then other fade biased clubs I've hit (9015d). The G15 is definitely more forgiving, no doubt, I'll hit it on the toe and still find the fairway and have decent distance. That said, it cannot hit the bombs that the i15 is capable of on normal to firm courses....the i15 is the longest driver I've hit...and I've hit everything (9015d, SFTP, R9 Superdeep, FT Tour, etc). Feel is awesome on the i15 as well, hit it on the screws and angels sing.
I realize you're asking about the i20, just giving background there. I hit one at the range about a month ago and think it more closely resembles/feels like the G15. Larger shallower head, more neutral face and bias. It felt pretty good, did seem to be low spin. I did NOT like the Project X shaft, just felt loose and actually seemed to "wobble" on some well struck shots. I'll be looking for an i20 in a year or so when prices drop, then throw my standard Harrison Saga 70S in it and compare to the i15 and 9015d benchmarks.