Boots depend on your riding activity to some degree. Just because you are riding a adventure touring bike doesn't mean you need adventure boots. Sport Touring will do just fine if that's how you ride. On the other hand, moving from sport touring to adventure touring on the Super Tenere I found myself exploring a lot more gravel and otherwise un-paved roads and locations. Changing to a more agrressive soled boot gave me more traction off pavement for the taller bike and better protection for any incidents that occur. My FJR was on it's side once in 160k miles, slipping on some sand backing out of a parking lot at 4 am in Jal, NM. The Super Ten has taking so many dirt naps I can't even hazard a guess how many times it's been on it's side.
It temps me to go places. Sometimes I screw that up at some point. Pick the bike up and go on. Good protection for the bike, and for me, make that possible.
TCX, Gaerne (I wear G-Midlands and find them easier to get on and more comfy than the Sidi Adventure Gore, plus they don't squeak!), Sidi, Forma, AlpineStar, etc. Lots of quality brands. Don't be afraid to push your price point up a little to get what you want. These are protecting a part of the body that is hard to fix and slow to heal.
The biggest thing I noticed going from TCX X-Fives to the Gaerne G-Midland was the improved traction and better support of the foot on uneven terrain. If I was just road riding, the TCX would have been fine. I still have them and wear them when I take our WeeStrom out for a spin as the smaller toe box is easier on the Wee for shifting, etc. I can walk all day in either.