If you don't think it is necessary to flashing a radio then don't do it. At least I heard that it will not make any difference to your phone storage and speed. But somehow if you have connectivity issues like drop calls, WiFi connection not searching or GPS is not seem to work than surely you need to flash the radio other than you are using at the moment.
If you want to see which radio your phone is working on is go to settings > About phone > Baseband version > See the last some digits and then search for your phone Like HTC desire lastest radio etc..
Note: I Recommend you should read more about Radio before flashing it. Sometimes there is a chance to brick your phone but don't worry if you have searched enough of it you will not going to loose anything. At least give a weekend or two to search for tutorials on forums like XDA, android central, Google, Wiki etc..
Happy Flashing