I've owned the 75B (similar to the 85B, but no ambidextrous controls) and the SP01 (not the shadow version) and regret selling both of them. They are a really good quality pistol for the money. The not only fits my hand well, but the trigger is the perfect distance so the first digit of my trigger finger sits perfectly on the trigger. I'm now in the market for a new one.
The 'B' is to denote the addition of the firing pin block. This is a safety device to prevent the firing pin from hitting the primer if the pistol is dropped. I believe the safety only prevents the trigger from being pulled, prevents the slide from moving and accidentally racking a round and stops the hammer from moving. The firing pin 'floats' in the bolt inside the rear of the slide and if the pistol is dropped there would be enough inertia to send the firing pin into the primer of a chambered round (in theory) if it could overcome the force of the firing pin spring (unlikely). The firing pin block is disconnected by a lever attached to the trigger bar. It is an added safety device.
Since the shadow is a competition firearm they have removed this block to make the trigger pull smoother. The shadow has a heavier front end due to the picatiny rail and will reduce muzzle jump for more accurate follow-up shots. I believe the sights are fiber optic as well. Grips are rubber and not plastic.
I like the idea of a working firearm and would prefer the firing pin block. The added safety is nice even though I'll probably never need it.
So, now I'm looking for a CZ 75B since I don't think I will ever attach a light to it or use it for competition (but I still could if I wanted to). I'll never shoot left handed so why pay more for the 85. If a SP01 or SP01 shadow should happen to come my way and the price was right I wouldn't hesitate.
Anyone out there please correct me if I haven't got my facts straight.