I know that the sub and the amp have to match but what is the difference in the two different subs and which is better

Electrical impedance (ohms) should match on your products.

Impedance needs to match.(or limits of amp)
If you had 2 2 ohm speakers in series, you could hook to 4 ohm amp.
Or 2 4 ohm speakers in parallel and you could hook up to 2 ohm output.
You can do a Series/Parallel and use 4 8 ohm speakers and amp will only see 8 ohms.

Less ohms is better but as said everything has to match and handle each other. I for example have a CV 10.2 (2 ohm) instead of the 10.4 blah

I would find equipment and amp that I like, and buy speakers to match Impedance,
Or find speakers that I like, an find amp to match.
I know it doesn't answer your question. I have heard good 2's and good 8's?