Last year I finally settle on my main carry handgun (G19), at this point I can say that I'm comfortable with the operation of the Glock platform but my full size gun is an M&P 9. Should I just keep the M&P or try switch to a G17 to keep things uniform?
I'm one of the weirdos that will carry different guns for different things. Though lately I've been using my Glock 26 as everything purely for convenience. All my DA/SA guns are decocker only style. So they are all common, the SAO action is pretty straight forward, and strikers are all fairly similar IMHO and are as close as I care to get to DAO. Yes I know Striker fired is not DAO but, shenanigans.
What ever you shoot best is what you should practice the most with and carry. I like having different stuff for when I feel like being different. However for carry I tend now to stick with one action.
There are advantages to using weapons of similar operation. There is no sin in owning multiple types of handguns, just be sure your fun gun is the one you have to stop and think about and not your fighting gun.
As mentioned up thread, variety is the spice of life, but it comes at a cost. If both are carry guns, then you need holsters, mags and range time with both.