ETSI[Europe] Regulations for 2.4Ghz ISM Bandwidth Limit and RF Power
I'm not saying EN300328 (Electromagnetic compatibility
and Radio spectrum Matters (ERM);
Wideband transmission systems;
Data transmission equipment operating
in the 2,4 GHz ISM band and
using wide band modulation techniques;
Harmonized EN covering the essential requirements
of article 3.2 of the R&amp;TTE Directive) is the document you need because your question is lacking in detail but this is a good example of 2.4 GHz transmission power and bandwidth requirements: -



Regards your other questions, you will have to read the data sheet for the devices yourself to ascertain what maximum data rates they can run at and, "which one is better?" - what does "better" mean in this context: -


Smaller?
Nicer?
Cheaper?
Easier to set-up?
More power efficient?


The list could go on!