Sorry for the long post. I'm mentally validating spending so much $$ on 5 holsters in the last year for my Glock 17.
I carry my Gen 2 Glock 17 daily. Buying one OWB holster ISN'T going to cut it because of the size of the firearm. (my opinion)
If I'm hiking, walking the dog, doing yard work, I found that my leather Side Guard Slide with approx. 5 degree cant (close to vertical) is VERY comfortable. However it doesn't conceal well because the length of the Glock 17 frame.
If I'm shopping or out and about, I use a leather blackhawk or leather Safari Land with higher cant angles for better concealment. (side guard offers these too)
If I'm in and out of my truck regularly or going somewhere I'm not sure if I can carry, I switch to a leather Safari Land paddle holster for fast removal without removing my belt. The paddle holster I have doesn't conceal very well and feels loose at times. I really need to snug up my belt with this holster.
If you can only get one, I recommend the Side Guard Slide with a medium cant. This should work for most occasions. I believe they are still only $60. They are made in Minnesota and are higher quality than MY other holsters.
http://www.sideguardholsters.com/
I do not have a Kydex holster...yet.
The size of this pistol requires me to "change" the way I carry with each holster and occation for best concealment with what I'm wearing.
Because the large frame Glocks are used my many LEO's, I have had EXCELENT luck purchasing USED holsters at gun shows and EBAY. They are already broken in and soft...cheaper too.
Good luck! (I'm glad you didn't ask about IWB also, thats another paragraph.)