B777 vs B737 water evacuation
 

I happen to compare water ditching evacuation procedures of b777 n b737 of two different airlines.

B777 overwing exit procedure requires leaving the wing towards the rear where as b737 requires survivors to leave towards the front, why? Any documented reference?

All I can say is good luck enforcing either one.

Only operator dependant, FWIW on our 777s with over wing exits (300s) the manuals say:

"Do not use the overwing emergency exit during ditching operations as there is no life raft installed"

On 737s I presume there are just slides on the wing.

Any other input on the topic?

Big difference here: The aim in the 737 is to get all pax into the water, while in the 777 they are supposed to board the slides rafts (and door 3 doesnt have one, only a manually deployed life raft if you pay for it). The 737 slides were never certified as life rafts

I have seen a FCTM for the 737-200 where it is advised not to use the rear exit doors in a ditching because of the tendency that that area will be under water. That paragraph not in the 737 Classics or NG series as far as I know.

Unfamiliar with 777, so only in reference to 737:
No slides on 737 over wing, all 737 slides are classed as slides not rafts, as per STBYRUD's post. Operators flying beyond 60 minutes from land are thus required to have portable rafts installed or carried in cabin, usually found in overhead storage compartment in centre of the isle.
Still applies to all 737 models, due to fuselage shape not enough buoyancy in aft to keep it above water within normal range of CG.

Also the A320 it seems, reference Sully on the Hudson.