The stock bed isn't removable, that alone makes a glass bed a must for me. Trying to pry off a stuck model inside the machine is a pain, and it screws up your leveling.

The blue build-tak the flashforge comes with works really well for both ABS and PLA, it's fine until it's been used a bunch then it starts getting finicky. ABS sticks really hard to it once it's been used a few times.

My advice is to use the printer as it comes and see what you don't like and let that inform your upgrades.