Yes, it is different.
I personally hate swimming in a wetsuit. It changes my stroke. I know it does, because I get this muscle in my upper arm that feels sore after I swim in a wetsuit. Very odd.
It will be easier on race day, because you won't have to worry about getting run over by a boat or something. On that note, BE CAREFUL! So dangerous swimming alone. If you don't already, it might be wise to invest in a Swim Safe belt.
I also find that in open water I can't feel the mechanics of my stroke like I can in a pool. In perfectly calm water I can feel everything about my stroke, the entry, the glide portion... I can find a nice groove and cruise. In open water, I can't feel any of that and I basically just go for it.
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"