I'll take at crack at it since these two are on my short list.
Cruise Control: GLA- adaptive, Audi - standard
Forward Collision Control: GLA - yes, Audi -no
Attention Assist: GLA - yes, Audi - no
Keyless start/stop: GLA - in Dec+ build, Audi - yes
Gear selector: GLA- electronic stalk, Audi - standard stick
Info screen - GLA - fixed, Audi - folding
Seating height: GLA lower than Audi (difference not available)
Leather seating: GLA - MB faux std & leather optional, Audi - leather std
Tires: GLA - extended mobility (no spare), Audi - conventional (with donut spare)
Exhaust pipes: GLA - dual, Audi - twin single
Hood: GLA - manual arm, Audi - hydraulic struts
Fuel consumption: not yet published but GLA will be better
Colours: fewer choices with the GLA in Europe, NA is tbd
Availability & build time for custom spec: hopefully soon but custom spec could be 6 months
I am still hoping that the actual 2015 Audi released will be upgraded from the announced spec to have adaptive cruise control (like the A3), but that is a long shot. It must certainly be on their list for the next model revision.
The standard features vs option packages of both will differ between. The price comparisons for a comparably fully loaded vehicle will have one being more expensive, but may be the opposite for the standard base or lightly configured spec. All this should be clear in the next month.