I think Clare
is perfectly fine though it doesn't get me excited much, in fact I find it rather dull. I had a best friend named Claire
when I was a child so I only knew of that spelling until my teens.
I am impartial between the spellings, the "i" makes little to no difference in my opinion on the names
I would have to say Clara
because the majority of the time I prefer names ending in "a" over their "-e" partners. And this is the same for Clara/Claire. I think Clara
sounds more vibrant than plain Clare
As far as I am aware it is not getting too popular, at least not in the region that I live, I haven't heard it in years.