heres a few quick differences between the 2020 and 2035 http

/homerecording.com/bbs/equipment-forums/microphones/how-at2035-superior-at2020-353299/
basically the 2035 is slightly superior and will have less background hiss. both are cardioid mics which have a pickup pattern directly in front of the mic in a heart shaped zone while rejecting much of the noise to the sides and rear.
as for xlr vs usb.. both can be used and neither is going to affect what sources the mic picks up as this has more to do with the pickup pattern of the mic, whether you use shock mounts or other equipment and whether you have noise cancellation or not. usb is more convenient for quick plug and play operation without requiring extra hardware however xlr and...