The only difference is the ballasts. AEL fixtures (2003 or later) use ballasts made by Advance (but with AEL labels and OEM parts like the ignitor board and slip-on wire connections) whereas the Thomas & Betts, FL Industries, and ITT produced American Electric stuff had ballasts that I assume they themselves produced (by the 80s AE ballasts had pretty sloppy windings). Other than that I think everything is the same except for the fact that AEL dropped the 113 and introduced the 115, which is basically a modified 113 with a deeper "hump" on the door, a heatsink on top, and a 2-bolt slipfitter. The socket bracket, reflector, latch, hinge design, door shape, terminal block, and PC socket on the 115 and 113 are all the same AFAIK. In fact, the 113 and 115 doors are interchangeable. The differences are so subtle I don't even know why they changed the name. GE has drastically changed some of their cobraheads without changing the model number and Westy dramatically changed the OV-15 and OV-25 to those boxy lights and kept the model number. The 113 to 115 changes are so insignificant they pretty much are the same thing lol.
I think the GE model that has changed the most without changing names is the M-250A2. It hasn't changed a TON but the housing has gotten progressively rounded since it's introduction in the early 80s. Also interesting is that aside from the M-400R2 and M-400A2, all the 400W GE fixtures have been called the "M-400" or M-400A Powr/Door" whereas the 250W lights were called the M-250, M-250R, M-250R1, and M-250R2. Not sure why they did it that way...
I always wondered why they changed the 113 to the 115 too. Seems it would actually use more material. Either way, I actually like the appearance of the 115 more. Also, I didn't know they made a boxy version of the OV-25...
The only thing I can think of is that the Advance ballasts required more clearance below them but I dunno. As for the boxy OV-25, yes, it looks just like our boxy OV-15s but physically larger and uses the round OV-25 glass. Those lights near the train tracks you said got missed by the LED crews (I think it was you) were boxy OV-25s. I personally like the boxy OV-15 better since the round OV-25 glass looks weird on the boxy fixture.
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I think the GE model that has changed the most without changing names is the M-250A2. It hasn't changed a TON but the housing has gotten progressively rounded since it's introduction in the early 80s. Also interesting is that aside from the M-400R2 and M-400A2, all the 400W GE fixtures have been called the "M-400" or M-400A Powr/Door" whereas the 250W lights were called the M-250, M-250R, M-250R1, and M-250R2. Not sure why they did it that way...