Folks will need to know your tank size, lighting, plant density, goals... to be able to answer that question.
Other things to consider is how likely you'l be to clean regularly (glass diffuser), almost never (reactor) and your tolerance for troubles (glass diffuser - simple, trouble free), reactor (potential for leaks, trapped gas....though once running fine should stay fine).
Ck the APC site as well for the Hagen Mini Elite style of inexpensive diffuser, as well as the new BOYU style here to catch up on alternatives. Plenty of info here to read, its a common question.
AB
AB