The obvious benefit with a large top turret is the reduction in time (range, turn dial vs range, look at chart, then turn dial). It takes a lot more effort to setup though, you have to print out the tape, then adhere it to the turret and make sure it's 'water resistant'. It does add weight to your rig (but shouldn't be a concern on a PCP)
The click chart allows for easy adjustments, but ideally your trajectory doesn't change often! The click chart can be easily lost/forgotten/stolen
? Some tape it to their stocks, but then it can then be awkward to look at.
I personally prefer an oversized turret. While Chairgun does have a feature to print one out, I really like the Scope Knob software: http://www.compufoil.com/product_sk.shtml
because there's lots of customizable features that improve my ability to read the turret. If you do get it, be wary of who you tell though or you'll keep getting requests to make them one