Hot enough for really good bonding seems to make bridging and overhangs difficult, any advice?
ABS and PLA, PLA being more forgiving.
ABS seems to love fan cooling, parts look much better and are dimensionally accurate, but is it costing all the strength?
being a noob is sorta tough! especially with fluid dynamics and thermal bonding!
There are numerous bridging and overhang calibration models out there. They can help you find the sweet spot.
Ross is right, its about finding that sweet spot or tailoring a config for a specific print. 
thats what I am trying to do… K better info, attempt 2.
Hatchbox ABS printing as low as 210c and 90c bed but getting great looking parts, just don’t trust them to be better than PLA for less effort given the temps.
I can get great bridging, perfect surfaces, but at the lowest temps for the filament and with less than ideal fill between lines, slight gaps in fills etc. Also a lot of fan cooling. I am trying to make printer parts in ABS and need the fill to be as much as possible and the layers firmly bonded.
Balance of acceptable fill and bonding produces bad overhangs, good overhangs seems not well bonded. can’t seem to connect the two. May have to rethink modeling in CAD for some of it. mouse ears and modeled supports might help raise temps to better bonding levels.
long term testing is a reliable solution, but hoping to mitigate as much ‘fail’ in that with some advice.
@AlohaMilton I designed the bridge model in the link below to provide a quick simple test for bonding strength between layers on non parallel vertical walls as well as bridging up to 15 mm and testing up to 5mm horizontal overhangs without bed heat affecting the bridge and overhang test. It might help you find a sweet spot.
Some slicers (Simplify3D) can be set to turn on the part cooling fan full speed for a bridge span and return to a minimal or idle speed (and possibly completely off?) for the rest of the print. Helps get a strong ABS bond and still retain good bridging.
To make sure I get good bonding between shells and infill I calibrate my filament for both its dimensional and thermal properties using these calibration clips: http://www.thingiverse.com/thing:1037301 Guarantees that I’m not under or over extruding.
After many tests and comparing I have returned to printing with PLA nearly all the time. It is quite hard and rigid and works well with fine details for my purposes.
@Jeff_Parish Thanks! I will check out the calibration models. Might have gotten a better handle on ABS tonight, better prints at least after venturing into layer separation territory and back again. Boy is that ugly and disturbing, whole layers lifting apart :oO Kapton is helping, was trying to use blue painters with ABS before which only works for small parts.