I know both worlds, having put 80k miles on the LT, and picking up a GTL in January.
I am 6'3", and yes, the stock GTL is a little more cramped than the LT. I think they lowered things to make it easier for "inseam challenged" riders to be able to flat foot the bike. I simply had more height added to my custom seat, and viola. BTW, I have had a custom seat on every bike I've owned.
For pillion comfort, my wife was not happy at first - at all. Lots more wind than the LT (we had a V-Stream windshield on the LT). Stock screen on LT AND the GTL both suck. Went with the full Aeroflow setup, and now she feels better protected on the GTL.
Maintenance costs - well, of course spark plugs are more, because there are 6...
The "maintenance costs being much higher on a GTL" statement hasn't seemed to be true yet. LT required "Major Service" every 12K miles and costs $700-$900. It's every 18K
on the GTL, and costs $800 - $900. Getting to the service areas (air filter for one) takes literally 10 minutes.
I do all my own wrenching (including multiple LT clutches), so I leave only valve checks and brake/radiator flush to the dealer (even on the LT - just don't want to deal with that part). If I leave that part to them, it's "only $300" for their part... GS-911 hasn't come out with a new unit for the GT/L yet, so if you want the "service reminder" light reset, you have to go by the dealer for the time being - it's a quick plug in, read and reset. They supposedly have a GS-911 unit in beta now, so soon home wrencher can do their own "inspection".
#1 issue for me was getting the Pillion Comfort dialed in; that's been accomplished. She never had an issue with the grab bars (she's 5'4", 110 lbs) being under her - and they re-positioned the grab bars for the 2013 model. On the 2012 model they were literally under the seat and useless. Maintenance costs are very similar. I had to do nearly all the same things to my LT as far as farkles (windscreen, seat, highway pegs) for comfort, so a wash there.
#1 reason I went with the new scooter? I thought my LT performed well, and it did. But after riding the GTL for 5+ months, I could never see myself going back. The GTL is now comfortable; I can easily do a 700-1,000 mile day just like on my LT; but the GTL simply runs circles
around the LT.