Well, to answer that, let me post a few pics for you:
My Rock River Arms LAR-15 Tac Op 2 .223 Cal:
My S&W M&P 15-22 .22 Cal:
My Ruger 10/22 with M1 Carbine Kit .22 Cal:
Now..... it all depends on what exactly you're looking for, or looking to do with your 15-22 or 10/22. Both are EASILY capable of being accessorized in many, many ways. It just depends on your flavor!
Starting with the 15-22, it's the same exact size as my LAR-15, and has the same functions. I use my 15-22 as a Trainer, since Ammo is considerably cheaper (<$20 Box of 555 Rounds of .22 Cal 36gr - VS - <$35 Box of 100 Rounds of .223 Cal 55gr).
You can change the Stocks, Rails, Sights, etc., and you can Add Scopes, Lights, Lasers, Slings, Rail Covers, Bipods, Grips, etc. LOTSA things to do with the 15-22!
The 10/22 has been around Forever and then some, and has a Cult-Like Following. I've seen many, many variations of the 10/22, and it still continues to amaze me, what some folks can do with these.
Mine was in the original Wood Stock when I bought it, and I added the E.A. Brown M1 Carbine Conversion Kit with Tech 100 Sights. It's now extremely accurate... more so than it was Stock... and the Conversion Kit was a simple, DROP-IN, Conversion. They also make an ArcAngel Stock for the 10/22, which gives it more of a Tactical look, and completely changes the appearance, IMHO. They look Great!
The 15-22 is usually priced between $350-$450, depending where you look, and the 10/22 is priced between $200-$300, again, depending where you look. I'd suggest taking a look at your Budget, and see what you can afford to pay for a New 22, and what you want to Add-On (..... and you WILL.....) when you buy it. Do you want to do a Short-Term Build, like the Weekend you get it... or do you want to do a Long-Term Build as Funds become available? It's all up to you! 22 Cal Ammo, will be the same cost for either the 15-22 or 10/22, so it's just a matter of what you're looking to spend.
Both Guns are VERY RELIABLE, and both have available High Cap Mags. Check the Web for Mag Prices, and that may sway your decision one way or the other, on which Gun to buy. Play around with Ammo Brands, as your Rifle may shoot one Brand better than another. I shoot WWB (Winchester White Box) Ammo, and it has worked very well for me.