I have the 420, and it is a great saw. . .mine was bought as basically a limbing saw, and has been used in sugar maple up to around 18" or so. After a MM and re-tune, it is waaaaaay stronger than any other 40cc saw I've ever run. In fact, it will give many 50cc saws a run for the money. As for the air filtration- my stihls at work have more of a problem with fine dust getting through the filter than my 420 (or my 7900, for that matter). You should easily be able to cut all day with no problems- mine has shown only a little dust on the filter after 5-6 hours of cutting.