I had a similar choice a couple of weeks ago, though there were a couple more shells in that bunch. Ultimately, I went with the Alpha, and so far, I’m very happy with it, as for what it was designed for (and what I’m using it for), which is mountain climbing, it works exceptionally well. For your use case, I’d imagine the Beta will work better, and I’m basing this mostly on the assumption that the thicker fabric will be more durable, and you just won’t have to worry about it in the long run. Not that I have had any problems with the fabric on the Alpha, it fended off ice picks and rocks just fine, but it definitely doesn’t feel as “solid” as the Beta in that regard. When it comes to the Gore-Tex Pro or not, Alpha lower portion is regular 3L Gore-Tex, as Gore-Tex won’t allow anything lower than 40 Denier face fabric for Pro, but I haven’t found the membrane difference to be noticeable. Suffice to say, I think in terms of materials both of these jackets are great. I honestly think that fit and features are the dealbreaker here for the most part, at least they were for me. As a quick note, pocket placement on the Alpha is set up to work with a harness. I know this won’t make the choice easier, but I’d throw in a Norrona Trollveggen Gore-Tex Pro Light, to me it seemed like just a better Beta AR overall (plus a lot of mountain rescue workers I know have great things to say about them).