If you physically compare the hummingbird, snapdragon, and OMAP processors you will find that they are all very very similar in core design. This is because they ALL use TIs Cortex A8 as the processor itself, with minor (or not so minor) differences in the FPU, memory controllers, and various parts as i mentioned in a previous post.
Sent from the Blue Falcon cockpit on my Fission 2.4.3 D2G
I didn't know you are talking about Snapdragon and Hummingbird also. Then of course, there are many differences.
For Snapdragon, it's different animal from the rest. You can think of step child from same father but not same mother. Though both Hummingbird and TI are from same source code for CPU core, layout and synthesis are different. Memory controller and peripherals are quite different as well.
However, if you compare processors of different numbers in same TI36xx family, it must be hard to find difference. I bet all are same silicon but different speed.