I am looking for a 1.5 side edge file guide for Line Prophets, moderately priced. Just finding 1 and 2. They are factory set at .5/1.5. What would be the benefits/ detriments of .5/2.? Skis are used for all mountain.
That is just silly. Side edges are tuned in whole degrees. You tune them to a 1,2,3,4 or 5. It is base bevels that are sometimes tuned to .5, .75 increments. Fixed guides are always best. Multi-angle tools are usually pretty suckie anyway so shine that idea on.
In all seriousness, what they do at the factory is not important.
A .5 is a bit much on an all mountain ski like that. I would think you would want a clean accurate 1 degree. And I would put a 3 degree side edge on them. No reason whatsoever to use a 1.5. The more acute the side edge the better the edge grip.
As far as base bevel, the less base bevel the faster you get on edge, which is great for a slalom race ski, but I would think not desirable for an all mountain ski.
Whole numbered dedicated side edge guides are the norm, but SVST does make a .5 degree shim. You could also add some tape to a dedicated guide to increase the angle. I'd be surprised if .5 degrees would be life changing on an all mountain ski, especially on softer snows.
I'd suggest that experimenting is your best option to discover what works best for you on a giving set of skis, terrain and snow types. It is very easy to adjust side edge angles or you could try setting a pair of edges to 2 degrees and the other to 3 degrees. Ski a few runs with 2 degrees on your inside edges, then switch the skis so the 3 degrees are on the inside edges to feel the feathering vs grip differences. Do this on different pitches, snow hardness and speeds. Then decide what you like best on those skis.
Having a small 'quiver of edge guides', guides with shims or a multi-angle guide is really nice to have so you can tweak your skis depending on your own preferences. Another advantage of more guide angles is that you can use them to measure and match existing edge angles. Just because the 'factory spec' is x, y or z, does not necessarily mean it's accurate. If your bases aren't flat, all bets are off anyway.
Honestly, I would say there's not more then 5 guys on this forum, who would notice difference between 98 and 94 degrees on side edge on icy courses, and on soft, I doubt there's anyone. Unless skiing on injected snow of course (and from this what I have seen in real life (unfortunately I haven't seen any forum members in real life... yet) there are very few who care ski normally there).
So personally I would say don't bother at all with this, and just use tool you have at home for side edge. There's really no difference how ski handles between 1, 3, 4, or 6 degrees on side when it comes to normal snow. On injected snow things are different, but I doubt many have chances to ski injected courses on regular basis. More acute angles do grip better in icier conditions, but they also don't last long, and that's why 3 degrees is sort of "standard".. it holds relatively long, and it still grips fine even on icier courses. But except for more grip there's really no difference how ski skis.
If you have to have 1.5 on the side (as many have stated 2 is pretty common unless eastern ice skiing and you may not notice any difference between 1.5 and 2), poor man's solution could be a strip of tape or 2 down the metal of the 1 degree if you do not want to go with the .5 shim. Mention of the FKTools plastic universal tool, use it long enough at the 2 degree and it may slowly wear enough of the plastic down to become a 1.5 degree. It is not as precise as the metal tuning guides.