This will probably get ignored because it’s solely a style issue, but I think the Minotaur costs more, looks cooler, has less hardpoints which can be used for either equipment or weapons and if you count the total number of either slots both have the same number, and at least from the designs I make has no need for that power output bonus, however that HP bonus the Valkyrie has is sweet. I find if I strain to use that 8% extra power output bonus I usually made a less optimal ship because of it. I can make the same ship with either hull models and I’m thinking of switching my main cruiser line over to the Valkyrie.
I been looking at some of the NPC Minotaur Ships and Remade NPC Minotaur Ship and Rebel Ultimate Cruiser, and NPC Minotaur would have to be redesigned, do to loss of power, so I guess 
oh well I can make the ship as is work pretty well.
Edit: I actually made a decent anti cruiser ship that uses the power bonus I am pleased.