i just recently moved from prodigy to 250d and 250d is MUCH BETTER HANDS DOWN!
1. bitfenix vents... only 1 dust filter under psu... seriously bitfenix? 250d gives you FOUR filters, under psu, on both sides of case and on front.
2. Non modular psu in bitfenix? Boy you gonna have bad time, been there done that. Got 605w Fractal Tesla gold+80 efficenty and i have to say, fitting this into bitfenix was nightmare! the holes for wires were so far away from actuall psu slot that i had to fit it in really ugly manner. On other hand no problem with 250d because rear of the psu slot is just wide open.
3. bitfenix tries to be normal atx wannabe case. So many hdd slots and i ask what for? If you gonna put there some good graphic you will have to take away most of the hdd slots in order to fit it in. 250d? no problem, hdd/ssd 2:2 slots are next to the psu slot so they are not going to interfere with anything. Protip if you dont use many hdds, take out one shelf, it will do a nice additional room for cables
4. inner design. in order to mount something like h100i you have to take out dvd bay on top which is pretty much **** when you have installed fan on front case. 250d? again no problem. In orded to fit there h100i you just take out the bay, mount this **** in and put bay back. It will fit.
5. size. 250d is 5-7 cm smaller but 2-3 cm wider than bitfenix
6. front of bitfenix case is ultimate dust catcher, if you put there intake fan it will choke loads of dust as there is no filter which is pretty sad.
On the side note, if you are going itx and as small as possible, good choice would be getting watercooling on cpu instead of traditional aircooling there are dozens of closed loops 120 mm setups to choose from.