I've got the Merf 3.2 and it's excellent, it features the 3 round burst setting which you can enable/ disable. To fully utilize the 3 round burst setting, you have to chronograph your rate of fire, or if there's a smartphone app that can also measure impulses, then you program the Gate MOSFET to your 3rd burst timings for your gun using the pre-programmed timings.
Have a look on Gates website and compare the features of each decide what you want out of it. Download the manuals for each and do a bit of bed time reading
Make sure you have enough room to fit it into your AEG.
Oh and I highly recommend you require your AEG with thicker gauge silicone wiring (visit component shop) 16AWG I think is recommended, and wire to deans to benefit from it.
Hope this helps.