In today's age of DVR and streaming, the days of serial being risky are dying. Serial worked quite well in Enterprise Season 3, and long story arcs worked well in DS9. I think DS9 would have been even more serial if it were produced today.
I'm good with either way as long as it's good Trek. But serial or long story arcs make for a richer series, IMO.
A lot of my own thoughts. I've also noticed that serialized seems to becoming more and more popular format. And all in all I prefer serialized series.
But I think Star Trek can be good with any of them. TNG is some of the best episodic television ever. DS9 is some of the best serialized television.
And Enterprise was absolutely fantastic with it's three parter-heavy format of the 4th season.