The current company is legacy-land as far as development tools goes (though they're reliable and in the right hands do very well). The prospective startup would involve new tools I need to "keep up-to-date".

I did a short (paid) project for them involving some popular scripting significantly-hipper-than-Perl language and delivered it in serviceable, idiomatic form that I know they were very happy with, using all the right libraries. I picked it up the tool/language quickly enough. I feel I need that experience and exposure to maintain my longevity in the SW market. Sticking with the current company is 2 more years I become more of a dinosaur.