OK. Here's your answer, but do make the right choice or I've wasted my time.
The 44 has a larger compressor cover that is optimized for the wheel. Thus, the 44 has higher flow and HP potential.
The 44 is a TE. Thus, the MAF duct attaches directly (clamps) to the compressor cover. There is no bell, no gasket and no (2) nuts. Everything is one diameter - there is no reduction in diameters as the air enters the compressor wheel. Conversely, the 49 is a TA and uses a bell - which IMO is ugly, and a penalty to performance.
I believe the 44 requires a modification of the wastegate actuator bracket. However, IME, it's always best to buy an actuator with the turbo, to be sure you get a proper, fresh actuator. Also, discuss wastegate options with your turbo supplier. For example, if you use a THDP, he will machine the wastegate in the turbo cover accordingly. Remember - discuss the wastegate actator, discuss the wastegate, or expect something may not fit or work as intended. Do it right. Do it once.
I recall talking to John Craig at Limit way back when about the differences between the 44 and the 49 and there were several little nits and nats differences which I don't recall and which others will swear don't exist. If you care, phone John for the blow by blow.
Good luck, and buy the 44.
Oh, the .63 a/r Garrett turbine housing will spool the fastest with the stock torque converter, but they are getting hard to come by. The .63 a/r PTE turbine housing will supply more top end, but IME the bottom end will be softer - you may not like it. Of course, this assumes your car is stock or near stock.
HTH!
strike
