The negatives for New Britain are obvious but the positives for Hartford are part of a cumulative effort that's been in the making for 20 years.
With minor league baseball, UConn's downtown campus, Front Street, lots of new apartments, the convention center, science museum, Wadsworth, the Bushnell, XL etc. Hartford is finally getting to the point where it may hit critical mass and take off. The idea of a ballpark downtown, minor league or not, is great. I would hope it would be built with historic character and be a beautiful addition to downtown that appears as if it has been there for years.
All of these projects, when put together, will provide the downtown foot traffic needed to really grow the city's core and create a consistent level of activity that creates an exciting environment. In short, if Hartford can build any large venue and have a tenant ready to occupy it, it is probably going to be good for the city. It is much better business than building a new XL Center and then hoping an NHL franchise will move in----though I realize that seems to be how you lure pro teams these days.