1. Alpine Touring (AT): This boot is designed to allow you to walk and climb, as well as ski. It is similar to a regular alpine ski boot that you would use at a ski area, except it has few key differences and additional features:
-rubber sole for friction while walking/climbing
-the upper shaft of the boot can lock into a forward lean position for downhill skiing or it can release so that your lower leg can move forward and aft with ease
-AT boots should be much lighter than alpine boots
-AT boots should be more comfortable than alpine boots
2. Telemark or free-heel: This boot is designed to hinge at the toe, which allows you to walk/climb comfortably as well as cross-country ski with a free heel. This boot also is designed for downhill skiing using either a telemark or parallel turn. Unless you are highly interested in the telemark turn, and taking that turn to its fullest potential, there is absolutely no valid reason to invest in any plastic telemark boot model, with the exception of the Garmont Excursion and the Scarpa T4. In the last five years, AT equipment has become so much lighter and offers so much more skiing control that the only reason one would endeavor into telemark gear is for the love of the turn itself.
That said, I have been a backcountry free-heeler for over 20 years and still do it, albeit less and less. I don't think there is much reason to use a heavy beefy plastic telly boot. Currently, I use the Merrill XCD Double boot with Rainey SuperLoops and the Dynastar Bigs for powder skiing. It is also important to note that I rarely, if ever, use the telemark turn. I ski these boots and skis with a regular old parallel turn.
For touring, light turning, and pack rafting with skis, I use the Alpine Sierra 75 touring boot. This boot works well for hiking on dirt and mud, it tours exceptionally well, is extremely light, and skis downhill acceptably well.
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More on AT Boots: Alpine Touring (AT) boots come in two different types depending upon which binding system you choose. The two binding systems are "standard alpine" and "Dynafit system." Some boots are compatible with both systems. Some boots are compatible with only one of the systems. In addition to some differences in the welt size and shape, the main difference is that the Dynafit system has metal holes on either side of the toe welt. The standard alpine binding system requires no holes on the boots.
The most important points for backcountry boots are:
1. lightweight
2. fit and comfort
3. functionality
Unfortunately, AT boot manufacturers still have not been able to satisfy all three of these points adequately for backcountry.
Weight: I won't even consider a boot unless it is super lightweight. This is simply THE most important issue for a backcountry boot. Most boots available today use heavy materials and have too many buckles and bells and whistles.
Fit and Comfort: Be sure to buy a boot with the lightest weight conformable liners. Also, a custom footbed is critical.
Functionality: Very few skiers, not even beginners, need a beefy high-top boot with three or four buckles in the backcountry. Two buckles are all that is needed. For most of us, speeds are slow in the backcountry, the snow is soft and forgiving, and we are not trying to carve to a speed record. Also, the other key item is the ability to quickly and easily lock the boot in a stiff forward lean position for skiing, and then quickly and easily release the upper boot so that it is very soft flexing fore-aft. You should be able to point your toe in front of you. The only readily available boot models that come close to fitting these criteria are Dynafit's TLT Race, TLT Light and Scarpa F1.
I currently use the Dynafit TLT Race boots. This boot is lightweight. This boot fits very well because I had them custom fit with conformable liners, custom footbeds, as well as some shell work. It also has a very unique fore-aft release that allows full range of motion in tour mode, and excellent rigidity in ski mode. There are however some design glitches in this boot:
1. the velcro strap is not durable nor is it positioned to correctly match hook and hair for maximum grip
2. in tour mode, the upper cuff of the boot must be pulled back so that it doesn't re-engage inadvertantly into ski mode. In this back position, it fills with snow while breaking trail in deep powder
Here are a few other boot models that I recommend:
-Dynafit TLT Light (unfortunately, the largest size made is Euro 28)
-Scarpa F1 (has some functionality issues)
-Dynafit TLT Evolution
-Scarpa Matrix
-Garmont Mega Ride
-Garmont Dynamite
-Garmont G-Lite
-Garmont Summit