I've been riding for almost over 18 years and in that time I can only remember 4 substantial pairs of adult boots. The first pair, I have no idea of the brand, just that they were black, probably Justin's. After a few years, I wore a hole in them that ended up tearing the boot. I distinctly remember this happening out of town on a Friday night practice before a cutting. I then got my next pair of brownish Justins which lasted me until the summer before my HS sophomore year. At the time, I thought both of those boots had been comfortable, then I bought my first pair of crepe soles. Holy cow what a difference!
The crepe soles were a pair of Ariat cobalt's, and I had made the leap to buying men's boots. My feet are huge (for a girl) and flat as can be. I inherited my Dad's caveman feet :( Switching to a men's boot helped with sizing issues a bunch. I really liked those boots and the first thing I remember about them was how heavy they seemed. The big problem was, at the end of the day, I could barely pull them off. Never figured out exactly what the fit problem was, but they were kind of tight across the spur-strap area, and the arch was too high for me. I had these boots for nearly 8 years, but the lining was junk after less than a year. I ended up buying lots & lots of Dr. Scholl's replacements.
Three years ago, I made a serious boot investment and bought a custom pair of Luchesse's staying with a crepe sole. Now I know how horrible all of those previous boots had fit me. These boots are amazing!! ZERO break-in. I can slide my feet in & out no matter how long I have been wearing them, and they don't slop around in the heel area. Plus, I have never had tired, achy feet after wearing them all day. I might buy another pair just so I have some "fashion" choices because I finally think my feet have quit changing.
I have been hearing great things about Rios of the Mercedes boots & I think I might try some of those before I buy anything though.
The only advice I can offer is to try boots on at the end of the day after you have been on your feet and running around; try on lots of different brands; try on some men's sizes/styles to see how different they feel from women's and definitely continue getting opinions on how they've worked for people who wear them.