Boost that to 5000 words. That takes your page to 25k download.
Add in background noise of say 50K and the difference between a small 300 word page and a monster 5000 word article is 50k and 75k. Add in gzip and the noticeable difference in speed of loading of those two pages is quite simply nonexistent.
Speed of your webpages is dependent on two things (and neither of them is the amount of content): server response time, and how much graphics crap you've got on your page. Those are the two things you need to address. And both of those, while they seem like small things to me, are 'fair enough' reasons to spank or reward (though I'm not sure if they're indicative of content quality. We'll take Google's word for it).
I can say that I'm one data point on this - my main sites rock speedwise. My crap sites are on $5 a year hosting plans which frequently are slow loading.