Holding my nose and voting for Jeb isn't the same as enthusiastically voting for him. Jeb isn't as bad as Romney but in no way do I want Jeb as the nominee. However, if Jeb gets it, I could see myself voting for him with no enthusiasm.
The dynasty argument makes little difference if Hillary is opposing Jeb. In all likelihood, such an election is either going to give to us Clinton term III or Bush term IV.
Your logic is precisely what the GOPe has been counting on for the last four election cycles. No more “holding our nose” or “voting with no enthusiasm” or “voting for the GOP even though they are worse liberals than the Dems”.
The Establishment thinks we are stupid for good reason.
As far as the electoral college and history are concerned they are identical.
I'd rather write in "no candidate on this ballot is acceptable".