Definitely action based, which is mainly down to one of my favourite gaming series', Fallout. Of course this series evolved from turn based, but let's be honest, most of it's aclaim came from its rebirth in 2008.
Anyway about the genre itself, I like the idea that you can do what you want, when you want and in whatever way you choose to do so. The sheer freedom gives you that real sense of adventure as you just set off and do as you please. Don't want to advance the main reason quest? Well that's fine, just go and level up first and search for valuable loot. Don't want to grind? Well you could always complete many of the fun optional side quests that usually come with most great western RPGs. I guess it's the variety as well. Sure a big selling point is the fact that you have the freedom to customise and mould your own adventure, but content and variety comes first in my opinion. You can literally get lost in grandeur of these massive overworlds and with so many quests and other miscellaneous tasks, the genre will have you playing for hours and hours and, well, hours. You certainly get your money's worth when you buy an RPG you're invested in.
The action part, which differentiates the sub-genre, also plays a big part. I've never really liked the slow paced patient sequences of turn based and strategy RPGs, I like the freedom to get involved in combat in whatever way I please. It just feels smoother in my opinion as if I can get my hands dirty in combat as well as choosing how I go about engaging an enemy.