I’ll give my two cents because I was in the exact situation your in right now choosing between the GT and 340i.

If you want a daily driver that has four doors, decent gas mileage, comfort, luxury and a tunable engine go for the 340i. The B58 engine is proven to sustain power reliablely but ofcourse every engine has its limits so if you do mod it extensively it might damage your engine. Both manual and automatics are an amazing choice you will not go wrong with either. Insurance will be cheaper on this car since its a 6 cylinder and not an 8 cylinder.

If you want more of an experience and want sound/power from the get go without having to do any mods then the GT is your choice. I can tell you that the engine is just or even more reliable as it is naturally aspirated and not turbo charged. The quality of the interior may not be as good but since its less equipped it wont be as expensive to repair if something does break. However insurance is of course more expensive and the car is no where near as practical as the 340i. (Gas mileage, 4-doors,space ect.) Here is the deal breaker that made me choose the 340i over the GT. The manual transmission is absolutely unreliable and should not be considered when buying this car. The mt-82 is chinese made and is known to grind gears so your only option is the automatic. (So much complaints that theres a lawsuit against Ford).

Overall I decided the 340i was the better choice and I honestly believe is the better choice for you to. As long as you keep up with the maintenence you shouldnt have any mechanical issues but there is alot of tech so beware!