Questions on first 6* choice

New question!

I got my MLB Paris for my first 6*, and I'm looking to either upgrade in time or to get a 2nd 6*. Do you all think it is better over the wide array of events to have a single really strong 6* or a bunch of mid-range 6*'s?

Also, on the topic of speed, Borage is an A speed with pretty weak damage. Is she worth it? A speed only helps in Colo/Arena, and I don't know if she is better than a good B speed with better damage. Both A's and B's are likely to go. Is she worth it upgrading to?