Yes, there are some advantages. The transmitter is the most important part of your RC aircraft system - it's the only part you can touch while flying! So even minor improvements matter.
Just getting away from the transmitter bundled with most RTF packages is a major step up in quality. Since you asked about "installing" it, I suspect you've already done that, but wanted to cover that for completeness. Everything feels a little better, most notably the gimbals will be smoother and more precise, and will return to center better when release. Those typically aren't programmable, which can turn an unwieldy, painful flyer into something really nice.
If you've got a Walkera Devo transmitter, you've already got most of those benefits. In all honesty, that will be easier to use than Deviation. The following applies to the last release (5.0), which I'd recommend for you. It may not be true for the nightly builds, as they are changing rather quickly.
Deviation has a completely different UI model. Well, two, actually. The "standard" mode is similar to Devention, but not as good because it hasn't gotten a lot of attention prior to the last release (that seems to be changing since). In particular there's no support for flight modes on modern flight controllers. If you're not willing to step outside of it and don't need the multiple protocol support, I can't see much point in going away from Devention.
The real power is in "Advanced" mode, which lets you do pretty much anything you want. The thing is, unlike Devention/other proprietary firmware/standard mode, it doesn't know anything about your craft. Instead of having setting for gyro control, throttle hold, etc. it gives you explicit control of the output on each channel, which some people think is more than the gain in power is worth.
There's almost certainly something it will do that Devention won't that would be useful. Sticky throttle holds are high on my list for any RC craft, including yachts without a motor. Got a camera on a gimbal and position hold? How about a switch to put you in position hold mode and let the cyclic controls control the gimbal instead? What depends on you and what you want to do, but there's probably something.
There are a number of ways to get a feel for this before you install degviation. You can download an
https://www.deviationtx.com/downloads-newemulator that runs on Windows
. Or look through the forums at the questions & responses. Or read through my
http://rc.mired.org/p/writing-deviationtx-model.htmlprogramming tutorial
