Q:
What is the difference between a Bilstein 5100 series shock and most other shocks?

A:
Valving. most shocks have a 50% compression and 50% rebound.
Bilstein uses a 30% compression and 70% rebound..what this means is a less jarring ride when hitting bumps and dips as well as
less "un-loading" of your suspension on the trail.

Q:
Is an "adjustable" shock the answer?

A:
No, if you get a shock designed for street and trail use like a Bilstein, the need for having a gimicky shock that requires air pumps and or crawling under your rig to adjust them for street then again for the trail...?

Q:
At what point do I need to step up to coil over shocks?

A:
The time is right when you would like the dial-in-ability and most of all, the performance of a coil over set up.

Q:
I've heard that with coil overs all the way around I can't have perfect street and trail performance?

A:
That is sort of true, there are give and takes with a
high performance suspension.
If built for street handling, you may wish for a softer set up for the trail..If set up for trail use only, if you do drive it on road, you may find it to be a little too soft.
The amount of Nitrogen charge in the shocks can help get you a happy medium.