In my opinion , yes.
FM2n(late model)
-syn. speed 1/250
-max-shutter speed 1/4000 sec
-all manuall controls with TTL center weigthed metering (60/40 balance); metering range EV 1 to EV 18 (battery powered).The camera will function without batteries but not the meter.
-Bright viewfinder system with aperture, shutter speed and 3-point exposure display (+ O -)
-Depth-of-field preview button
-Nikon F lens mount .
-NOT TTL flash
FM3A:
-Exposure modes:Aperture-Priority Auto; Manual
-Compatible Lenses:Ai, Ai-s, AF-D, AF-S, P -(except IX and G-type Nikkor lenses)
-Metering System: Through-the-lens (TTL) 60/40 centre-weighted full aperture exposure metering system using a pair of SPDs (silicon photodiodes) and metering IC circuit.
-Metering Range: EV 1 to 20 at ISO 100 and with f/1.4 lens (i.e., from 1 sec. at f/1.4 to 1/4000 sec. at f/16)
-Exposure Meter Coupling: AI type
-Exposure Compensation : Exposure compensated in ñ2 EV range, in 1/3 steps
-Auto Exposure Lock : Auto Exposure Lock
-Film Speed Setting : DX: ISO 25-5000 with DX-coded film; manual ISO 12-6400
-Shutter : Vertical-travel, metal, focal plane shutter with aluminium alloy curtains
-Shutter Release : Electronically controlled in A mode and mechanically controlled in M mode; center-threaded shutter release button accepts AR-3 Cable Release; button locked when film advance lever is flush with camera body
-Shutter Speed Range: M Mode-1/4,000 sec. to 1 sec., B (Bulb), A Mode-1/4000 sec. to 8 sec. (stepless control) 14 discreet settings in all
-Sync Contact: X-contact only; flash synchronization up to 1/250 sec.
-Flash Synchronization : Built-in ISO-type hot-shoe; threaded sync cord terminal provided for off-camera or multi-flash photography; synchronisation with electronic flash units at speeds up to 1/250 sec.
-Flash Ready-Light : LED provided; visible inside viewfinder; lights up when SB-28/28DX, SB-27, SB-22s, SB-16B or SB-29 Speedlight Unit used is fully charged; blinks to warn that the shutter speed set is beyond the electronic flash's sync range or for full output warning
-Accessory Shoe : Standard ISO-type hot-shoe contact (sync contact, ready-light contact, TTL auto flash contact, monitor contact, GND), safety lock hole provided
-Self-Timer : Set/cancel mechanical type provided; approx. 4 to 10 sec. duration
-Depth-Of-Field Preview Button : Stops down lens aperture when pressed
-Film Advance: Single-stroke type; 30 degree stand-off angle and 135 degree winding angle
-Film Rewind : Manual via rewind crank
-Motor Drive Coupling: Electrical contact and coupler built in for operation with Motor Drive MD-12; the MD-12 is operable when film advance lever is flush with camera body
-Multiple Exposure : Provided; disengages frame counter for correct count
-Power Source : Choice of one 3V CR-1/3N lithium battery, two 1.55V SR44 silver-oxide batteries, or two 1.5V LR44 alkaline batteries; optional Anti-Cold Battery Holder DB-2 accepting two 1.5V LR6 (AA-type alkaline), 1.2V KR-AA (AA-type NiCd) or 1.5V R6 (AA-type manganese) batteries available
-Exposure Meter Switch: Lightly pressing the shutter release button switches meter on; meter stays on for approx. 16 sec. after finger leaves button, then automatically switches off; meter automatically turned off when shutter speed dial is set to B
-Camera Back : Pops open when the film rewind knob is pulled up; detachable and interchangeable with Data Back MF-16; film cartridge confirmation window provided
To me the main advantage of the FM3A( more like in the the family of the FE2) is the AE,TTL flash and the new hybrid shutter, plus the advantage over the FM2n od DXcode reading and the window that show you what film are you using( no more reminders tabs on the back of the camera, but I hear that the back plates are interchangeableas and some peoples are addapting FM3A back plates to their FM2n).
There's is one reality, being discontinued the FM2n , I opted for the FM3A ,not only for its versality, also because in the future parts will be more accessible in case it needs repair.
Another thing that is that the viewfinder screens(3 types) that are offered with the FM3A are quite more bright than any other in the Nikon line