Hey V-Tec, my vote is for the 300. Bought mine 3 years ago, it was "new" never sold '04. Just got the 450 FSE '05, new as well, never sold.
I'm an old guy, 56 and all of 135 pounds on my 5'9" frame. Been riding since I was 13 or so. My list of dirt bikes is quite long and crazy. Recently the ones in the shed, all at the same time were, CR250R (bad ass, built to the gills, all the "good stuff"), KX125 (awesome), CRF230F, CRF230L CRF 150, CRF100, Yamaha DT100 '83 (daughters) and the EC 300.
Got rid of everything except the 230L and the EC300 to get the 450FSE. We decided that having tags was important.
I can not tell you how much I love my EC 300. It pulls like a tractor and feels light as a feather (to me). Not like my old KX125 but riding the "Ting Ting" is effortless. I have not had a "legitimate" crash on her. The kickstand from Hell has made her fall over a couple times but as to actually crashing, nope, not yet. Of course I only have 4500 miles on her so it's still early
.
I've had zero problems and the engine seems as good as new. Never fouled a plug and they look "perfect" when I change them out of boredom and feeling the need to "do something". While the subject of oil ratios always causes discussion I'd like to say "do what you want, I run full synthetic (any type) at 28:1" I NEVER, I repeat, NEVER go less than 32:1 regardless of what the manufacturer says. I also have never seized a motor. My KX and Bunny (CR250R) loved 20:1 the Gasser seems to prefer 28:1. Never fouled a plug in any of them.
The suspension is actually too stiff for my weight but since I can drive it like Charlie Daniels can play a fiddle I have been reluctant to change it. The 450 is actually closer to "correct" for me, go figure!
I have the big power valve cover and the flywheel weight (mine is actually a DE, with the light flywheel) but prefer the engine w/o them.
As I typed this I realized there is not a single thing I can think of about the 300 I dislike or would change. Even the suspension being a little stiff for me is not an issue and it may have saved me.....I was alone in the woods at the state forest (bad idea, the alone part) cruising down a trail at decent speed and came up on a series of "bumps". I hit the first one at maybe 30mph and found myself about 10 feet above the ground!!!!!! Took me by complete surprise....the Ting Ting's suspension compressed fully on impact. The next bump came fast but the trail did not drop straight down after it. Went straight to the car and came home. Riding alone in the forest was as bad an idea as my wife said it would be. I was shaken.
I credit the Gasser for saving my butt on a jump I'd never do on purpose.
Go for the 300 and never look back!
Ed