I have the Yamaha DXR12, which is similar to the ten and love it, but seldom need to use it. I have unpowered head. This is what is called the FRFR method, that is using a fairly flat powered speaker to amplify your sound. This way, the Yamaha or similar product won't color your sound much. Thus a fender twin amp with a fender twin 2x12 cabinet still sounds like a fender twin amp with a fender twin 2x12 cab, just like it would if you put a mic up to a real fender twin w/ 2x12 cab and pumped it through a PA. The Yamaha DXR is a PA speaker, so what you hear on stage matches what comes out of the PA system if playing live.
You'd want the Powered head if you want the option to play through a real guitar cabinet. The negative to this is that a real guitar cab sounds like only one guitar cab. In other words, you can turn off the virtual cab sound in the outputs going to your real cab. However, let's say you have a Marshall 1960 cab on stage. You dial up a fender twin amp. You'll want to turn off the virtual cab in the Kemper. Now you have the sound of a fender twin amp going through a marshall 1960. If you leave the virtual twin cab on, you still have that sound additionally colored by the Marshall 1960 cab. Keep in mind any profile you find was tweaked and created to sound the way its supposed to through the guitar cab it was created with. This doesn't mean that great sounds can't be found and tweaked, it just means that everything you play with won't sound as it originally intended, as your real cab colors it.
I'd say, go with the Yamaha DXR10. If you already have a cab that you love or committed to, then you'll want to go with a powered Kemper, as it's the cleanest and easier way to power a real cab. otherwise you'd need some sort of external amp to power your cab. Also if you buy a powered Kemper, you can always use it with the Yamaha, as it also has the unpowered monitor when output. That way, you have any option you want. You can hit the road with just the Kemper head and power the house cabinet at any club with your Kemper. However, when you're able to bring your DXR 10 with you you can use that. Keep in mind that it sounds like you don't already have a good cab you are dedicated to. In this case, if you went the powered option for the sake of using it with a good guitar cab, you'd have to buy that as well, as the spider speaker is not going to give you as near of good tone as going with the DXR10 or similar quality powered monitor. It's also extremely portable