Putting aside the company differences (China VS Japan), GBBs are generally more finicky and require more maintenence then an AEP. They also are greatly affected by temperature, specifically when playing in the cold, an AEP will do you better.
On the other hand, the feel and realism of GBBs can never be had in an AEP, nor can the velocities most gas blowbacks output, nor the trigger response.
If you want a high quality, well performing, and durable GBB, go for one of the latest TM ones, such as their Hicapa series, their Glock 17, and their latest 1911 variants.
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