Definitely television. That's something I could definitely get behind. Having a seperate feature film series could be confusing, in the same sense that Smallville and Superman Returns do not exist in the same universe. Having one on the big screen and one on television helps to clarify the difference.
Besides, if you plan to stay truly faithful to the original series it just wouldn't look right on the big screen. You make it work for much less money on TV and keep it faithful.