6'3" here. I ride 183's and I like to keep it around 180-185. For me, 191's would be too much for a park ski. It's doable, but that's a lot of ski to try to whip around if you plan on spinning, especially if they're 100 underfoot. If you like big, floaty tricks and you're going to split your time between park and the rest of the mountain I think you'll be fine.
Going to add in here to counter above. Used to ride 181s, got Kartel 186s and I've probably ridden 90% park this far and love them. Wood length 190, straight tape 186.3... i wouldn't be concerned about 191
I'm 6'0 and I ride the 191 95's, way sick definitely get the 191. The soft flex and the rocker makes them ski short and on the 181 I washed out a decent amount. The first few days you might feel like they're a bit long but you'll come to appreciate the extra length 100%