I agree with what Neuro is saying, to me, either writing or reading, the most intersting part of science fiction is the impact the tech has on the world/universe and the people in it, not so much how it works.
Also just because something is set in space doesnt mean it has to be super sciencey, just look at Star Wars. Most of the tech in that universe has been around for a long time, its just part of that universe. Heck you even get some magic thrown in. Its not hard or real science fiction by any means, but its awesome =)
So for your example about communication, think of what your setting would be like without FTL communication. To me it brings up images of a pre telegraph western setting, when letters had to be delivered and sending a message and getting a response could take days or weeks or even longer depending on how far that message has to travel.
That has a large effect on things like deploying military forces across a large region, tracking/catching criminals, the way planets communicate with each other.
All of those things change if you have FTL communication, its a minor detail that totaly changes the way tons of things work.
Either of them can be done well, but take some time to think of the effects of your tech choices and what kind of story you want to tell before hand.