If that's your point of view, then you may as well go for
the better bikes. There is a qualitative difference, and
this difference simply gets more pronounced with the
quantity and quality of miles.
You may want to also post details on the kind of
components you're looking into (eg, 105, Ultegra, ...)
and get some opinions on that, if you care. These are
mostly standard, but they do still vary year to year.
If by "vacations" you mean to also include touring, then
issues like gear ratios become even more significant.
These bikes are close enough to serious race caliber
that they're built to survive a Grand Tour. I don't think
you need to worry about New England destroying them.
Of course, you may want to keep the Cannondale in good
shape for the ugly commuting days -- with a new bike that
nice, I'd be wary of mucking it up with winter gunk.
Are you getting a fit-kit? If not, any reason why not?
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