Your list includes two kousa dogwoods - Satomi and Heart Throb - the interspecies Stellar series and the Cherokee series which consists of selections of the native American cornus florida. There are very few successful plantings of cornus florida in Maine except along the immediate coast, so I would cross the Cherokee series off the list for Z5. The Stellar series and pink kousas are possibilities, but once again I'd suggest you check with county extension, U of Maine or one of the large Maine nurseries for their recommendations. The sad truth, though, is that no pink dogwood is likely to be a very robust grower in Maine's Z5.

I don't think performance in the landscape is related to bract color - sorry if I was misleading. There are just many more white kousas than there are pink ones so selection for vigor and other desiireable traits has had a much wider field to work in.

1. As far as I know there are only three pink kousas in commerce, Satomi, Heart Throb and the impossible to find Beni Fuji. If you think about it, every pink kousa in existence derives from a find in the wild. If that original genetic material is adapted only to mild areas all the pink varieties will be adapted in the same way. Some white kousa genetic material likely comes from higher altitudes and harsher climates. Thus some white varieties will do well where pink ones cannot. I do know of an extensive planting of Satomi in Maine. Probably at least a dozen along a property line. You can easily throw a rock from the last tree into a salt water cove, though, so it is an entirely different climate than yours.

There are a few more pink cultivars on the market - Radiant Rose, Ruby Slippers, Fireworks. With the exception of Beni Fuji, the color looks washed out on all of them, IMO. I would go with a white flowering one - they seem to be much heavier flowering......and many times with good sunlight the white bracts age to a pink color anyway.