Filter type is a personal choice not dictated by tank size, however that sounds like a very large tank and I'd be surprised if an external filter was not the best choice if you can afford it.
external would be better , you can get some unbranded ones from ebay for £43 delivered , i've been running 1 for 2 months with no problems , was looking at getting another one
1200 lph
you could have 1 external (1200 lph) for £43 delivered and 1 internal (1000 lph) - tetratec in1000 for £23 delivered on ebay