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I have stayed at both locations and had a great time at both. Accomadations at both locations were comparable but a little more expensive at Grand Lake.
Riding was much better at Grand Mesa, in my humble opinion. Grand Mesa was more of a boondockers heaven, miles of varying terrain for all levels of experience, mostly fresh powder everyday we were there. Barely saw another track in the snow.
Grand Lake is also ok but is mostly built around a system of trails accessed by everyone, so, alot more folks. You don't have the multitude of open fields and inclines to yourself, like you do at Grand Mesa.
Nightlife; at Grand Mesa it is simply you and your riding friends. If you stay at TML you grab dinner in the lodge, have an adult beverage at the bar, and then perhaps sit next to the fire for a bit and then hit the rack to get ready for another day of great riding. At Grand Lake, you can ride into town (if the snow copoperates) where you have multiple fine eateries and a couple of different places to have an adult beverage; nice little town that truly accomadates the sledders visiting.
Accomadations; TML is located off the beaten path a bit. The owner who is a fine person and works really hard to make sure his guests are comfortable and have everything they need to enjoy they stay, is also working hard on completely redoing his accomadations/cabins. The ones that have been finished are looking very nice. You would have to contact them to see where all that effort is at. In grand Lake, we rented a house with a few other folks. You really can't compare the two but in Grand Lake you definitely have a whole host of options.
It all depends on what you want out of your trip. There are rentals at both locations if needed. Both locations can be "ride out" depending on the snow; I would say Grand Mesa for sure at that time of the year, not sure about Grand Lake.
Bottom line, if I had my choice, I would go with Grand Mesa for spectacular riding. I would also suggest TML for my destination. Folks who go there are a bit more serious about riding instead of anticipation of a wild night life, although, don't get me wrong, the crowd at TML ride hard and PLAY hard.
Drop me a PM if you have any questions.
Chaos