I've only used the Shimano Sustain in my favorite gear shop, a little too pricey for me, but it sure is smooth. I use the Shimano Spirex 2000 front drag on rivers. I like the paddle handle for when you set the hook and the fish comes at you, easy to find and crank.

I also like the trigger finger casting feature, particularly during the winter so you don't have to use both hands (one to flip the bail). These systems are most effective without anti-reverse allowing the bail to circle back to the top. A lot of folks would rather have the A-R, but I prefer the trigger.

Go with the front end drag. There is a noticeable difference in smoothness. Well worth the less convenient access, in my opinion.

The 2000 works great for 8-10 lb test, but if your going heavier, I'd go for the 4000. Love shopping for gear!