stronger internal color correction (tracking and roto)
Colour
DaVinci Resolve is free for what you need (doesn't sound like you're doing anything larger than 1080p) and FCPX does have colour and shape masks which can be keyframed.
and stronger audio editing tools. Sound track pro has a much more polished interface for higher end audio work.
Audio
Nothing is stopping you from using Soundtrack to edit your audio for FCPX, but you'll have a smoother workflow with Logic, since it supports FCPXML import, respecting roles and subroles. Pro Tools, Digital Performer, Sound Forge, and Adobe Audition don't do this without a workaround or 3rd-party tool.
AE vs Motion
I find that I'm doing the same stuff I did in After Effects at lightspeed in Motion. Things that would take a guaranteed half-hour with AE are done in ten minutes with Motion. Loving it for video too, Motion's Optical Flow slo-mo is better-looking than anything else on the market including Twixtor. Great motion tracking too, which has been just as good as Mocha in my experience. The behaviours are such a huge time-saver - have you looked into the equivalent for AE? Expressions? What a mess for those of us just trying to get our ideas from our head onto the screen.
Software $$$
I would stay as far away from Adobe CC as possible. Renting software is not good for users, only good for Adobe. Don't look at your FCS as a $1300 investment which you still need to recoup - I'm sure you've made that money back by now, right? The people vouching for Premiere are really doing themselves and others a disservice - look for ulterior motives there. Once you're paying the rental fee, you're stuck. If you want to access or open your old projects, or if a client comes back for an update, then you need to keep paying the rental fee.
FCPX: Avid and Adobe will be playing catch-up for the next ten years
If you have any Final Cut Pro X questions or are stuck, I'd be happy to help out if needed. It really is the future, for almost all pro video applications. The TED talks and conference have switched to it as well, due to its metadata power.
Oh, and good luck with the install!