I've been using QGC, MP, and Tower for some time. Just purchased Solex + Missions last week (partially due to curiosity and the raves it seems to be receiving in these forums).
Since I've switched from a Windows tablet to Android (Dell Venue 10, 5.1) MP has fallen to disuse.
QGroundControl (QGC)
- Free and open source
- Multiplatform: Win, Mac, Linux, iOS (beta), Android
- Currently maintained, 2-3 main contributors
- Has surveys
- no spline surveys
- sometimes surveys load from saved missions as individual waypoints
- Planned Home and RTL paths shown on map
- Geofences are defined per mission
- (Likely a user error on my part) Requires extra confirmation at mission start, causing false error
Tower
- Free and open source
- Android only
- Not much project activity since Oct. 2017, 2-3 main contributors
- Does not have surveys
- Pleasant interface and generally easy to use
- Takeoff and RTL planned locations not shown graphically on map
- (Some people prefer this, whereas I prefer the QGC approach)
- Allows fully autonomous takeoff for missions
Solex
- Proprietary, $30 for main program + $20 for missions + $10 for geotagging
- draws heavily from 3DR Solo and Tower open sources
- Android only
- Currently maintained, 1 developer
- Has surveys and spline surveys
- Has lots of advanced waypoint actions that leverage Solo/OpenSolo advances
- Beautiful interface and generally very easy to use
- Takeoff and RTL planned locations not shown graphically on map
- (Some people prefer this, whereas I prefer the QGC approach)
- Has integrated firmware upgrade capability
- IN MY VERY LIMITED EXPERIENCE WITH SOLEX seems to have lots of little quirks, usability challenges, and bugs. To be fair, I have not yet flown with Solex (not quite confident that I should).
- Developer might be busy/vacationing... hasn't responded to my reported issues or offers to help
Just my 2 cents. I appreciate that each of us have different needs/experiences/opinions. What's great is that we actually have many different choices for ground control apps.