Let me start out by explaining I have been instructing adults and children in riding and riding safety for over 17 years so I a little biased. I do believer that if you follow some very simple guide lines you can have the best of both worlds.
The main guidline is to have a smooth sole! There is a REASON for this. The reason being: slip safety. You do not want your boot/foot getting stuck in the stirrup. Smooth soles allow the boot to slip if there is trouble. Many boots like the Ariat FatBaby brand are more fashion boot and causal wear then they are a riding boot. With the heavy amount of tread and the widened sole you can get stuck in a stirrup very easly. This could be very dangerous.
Guidline number 2 is to make sure that your boot can fit into the stirrup with room remaining on each side! There are many brand made that are very wide/ square cut. If the boot can not fit into the stirrup at the ball of the foot then you need to choose a different boot for riding.
These guidlines should be followed for either English or Western riding. Safety is a very important part of riding and being able to enjoy your horse for many many years.
Be happy, Ride safe and Ride Often!