to clarify, you mean something like this is better right?
serv_info = service_info(service)
if serv_info.nil?

BTW, I should add that the non-native meterpreter code that I've been working on for about 2 years now sadly, improves the services post API significantly and he could just use service_exists?(service) if I can get it merged.  It will require significant time from egypt tho, and will probably have merge conflicts since I haven't touched it in quite a while.