I'm in a similar position thinking about going back to school, but I admit I'm confused about the question, because the programs I've looked at won't consider masters' students unless they have a bachelor's in CS (or equivalent, which there are nontrivial requirements there). So from my vantage point it's always been going back to do a second bachelor's.
I have a lot of programming experience, and a lot of statistics/numerical computing experience, but not so much experience with more hardware- or low-level networking stuff.
I would not say the same thing to someone who already has a BS in CS; but for someone looking for a career switch like you are, it makes a lot of sense.