I was just out in 25 knots of wind and peaking gusts at 30 in a 5.8 and my go 139 in knee high chop and I was fine. The Go 139 is a fast board. I wish thy would make one with inboard and outboard settings for the footstraps. Only complaint.
But the Go is a fast board with the right technique and sail size. I found the sweetspot for it to be a 6.6-7.6 sail. It might take some getting used to for balance at first, but 80 cm is pretty wide and it has pretty full rails for stability. Hell, I tried my friends 105 L hypersonic and could uphaul, waterstart and go fast too.
Id say go with the Go. for learning, its just that bit toughter than the carve, allowing for more spectacular wipe outs when you find your nose diving into some chop at 35 km/h