I did a head to head comparison of the most popular apps to see how they stacked up for 9 runs tonight.
Slopes, Trace Snow, Ski Tracks, and Maprika were all running. I attached screens from the results.
Trace Snow has some cool online features with the website, as well as being able to join local groups, and the leaderboards are interesting as well. I think it's the one thing that sets it apart. It's pretty solid in terms of accuracy, and tracks similar stats to the other apps. The one thing that might be of interest to park folks, it tracks jumps, which I believe is unique to this app. The puck is interesting, but as a skier I don't want to attach it to my skis and the app does a good enough job without it imo for free.
Slopes is straight forward and simple to use app, and has similar stats to Trace Snow. I like that you can trim your session for those time your drive off and forget to turn it off. They are adding the photo tracking, similar to Ski Tracks. Good social media interaction, and the posts look good on FaceBook. It's great on the iPhone, interacting with the native heath tracking, and works with the Apple Watch (which I don't have). The non-subscription version provides lots of features, and I don't see any major reason to upgrade and pay for it... unless you like the 3D interactive maps and speed heat maps and other cool map features. Those features do set it apart from the other apps if you're willing to pay.
Ski Tracks is for the data obsessed for sure. Tracks all kinds of stats, some of which aren't really needed, but it's still cool to know. Sometimes those deep stats aren't totally accurate though (for example, it said I was on a 43 degree slope and it's probably more like 25). I like the photos on the tracked runs. UX could use a little polish, and it would be nice if it changed the color of lifts versus runs on the map, but if all you care about are the numbers, this is numbers city. The Ski Tracks Lite app, which is what I used for this test, allows up to 5 runs tracked, otherwise you have to buy it.
Maprika doesn't track stats, but it does a nice job of using the map of the resort to overlay. There were some minor accuracy issues but that's a signal issue that all the apps had. It would be cool to see some of these other apps use the resort maps also, as it's much nicer looking than a Google ariel view (which is often a photo that isn't even during the winter).
I've tried SnoCru in the past, and didn't include it in this test. It's a nice option if you have a lot of friends on the mountain at the same time as you, otherwise I think the other options might be better.
Summary
All in all, they are all pretty good. Each have pros and cons.
All of the apps (minus Maprika) measured speeds within 1mph and were all fairly good in that way.
They all had some issues with reporting the position I was in to a degree on particular runs. Most of that is likely related to the strength of the GPS signal, but none the less, I think the apps should do a better job of snapping your position to the known trails (as an option if nothing else).
I think it comes down to whether you value the numbers (Ski Tracks), the social media interaction (Slopes), the leaderboards and website option (Trace Snow), pretty looking maps to capture the day (Maprika), or an ability to find your friends for the day (SnoCru). I would imagine for some folks, it's an easy choice because they value certain things higher than others. Personally, there are things I like about all of them and wish I could combine them all into one super app.