The La Sportiva Boulder X Approach Shoe is a well built, sturdy and very useable shoe. After testing the shoe in a variety of trails and mountains, I have found this shoe to be my new go-to shoe for my performance days. I will compare this to the Merrell Moab Ventilator to give a clearer understanding(because it is a well known shoe by many people including myself). I am an experienced and active hiker and climber.
Cushioning: The Moab feels very soft cushy, but under closer inspection that may be because there is simply less and softer cushioning. The Boulder X has slightly thicker and more useful cushioning. The softness of the Moab can lead to foot movement under hard use. In the X, my foot did not experience that annoying sliding which an lead to ankle problems. But many people will enjoy the softness of the Moab.
Fit and sizing: I believe the Moab sizing was corrected over the last year or so. Previously, I could not use an after market footbed without going to a larger size. I can now use the footbed (Spenco is my choice) while also using my correct size (10.5). The Boulder X sizing is a more useful size for me. A 10.5 is actually sold as a 44, which gives you an extra millimeter. But the X is slightly more narrow up front. That could be an issue. I like a wide forefoot and after market footbeds. I could not use the Spenco footbed in the X. But, I am surprised that the original footbed in the X is the first useable one I have seen. I just added a small amount of mole skin under the arch and I am happy.
Flex and Movement: The Moab is very flexible. But you quickly find that it may be too flexible for some serious trails or mountains. The Boulder X seems to have flex points in just the right spots. I was able to move very easily and quickly with the X.
Grip: The X is clearly better. The Boulder X gave me good grip on all rocks. Remember, always be careful while descending on wet rocks. The Moab is average in grip on dry rocks - there was little grip on well worn or wet rocks. The Moab sole will last for many miles. I personally need the kind of grip found on the X.
Comfort: I thought the Moab would always be better here due to the softness and flex. But I am very taken by the X. It is plenty comfy and still very useable on the trail.
Break-in: The Moab has essentially none or very little. But it is too soft. The Boulder X had very little break-in time. I am a blister king and have had no problems with the X break-in at all.
Weight: The claimed weight for the Boulder X is an ounce, or so, heavier per shoe than the Moab. Seriously, I never noticed it. I have used the shoes on mountains and trails. I have also used it for trail running. The weight was never an issue or even noticed. That may be because the X rolls and flexes at the right places. The Moab is just plane soft everywhere.
Construction: Both are well made. But the X clearly is a more durable shoe. You will have fewer issues on rocky mountainous terrain. They did a good job making the X.
Both shoes are very good, depending on the application. I enjoy using the Boulder X more that the Moab and am now converted. The Moab is still my daily shoe for light training. The X is my shoe for serious days and serious mountains. You will not be frustrated with your purchase. I would like to see the La Sportive Boulder X give a millimeter of added width up front, but so far it is good. Most people will not have an issue with it. My feet are a bit wider up front.
After even more mountain use, I am finding myself catching the toe on one of my shoes. I switch between different shoes, so that could be related to a slightly longer toe. I have also turned a ankle (no sprain issues at all) a couple times. I seem to need to tighten the shoes very much to gain precise control on the downward route.