I do a lot of planetary imaging from Sydney, and have in the last year switched from Newtonian to 14in SCT, imaging near 10m f.l. Light pollution doesn't matter for the planets, obviously it's a serious issue for deep sky, I'd imagine that doesn't really change much with scope type, but will with focal length (?).
While seeing is crucially important for getting the best planetary shots, there's no point in only waiting for the perfect nights, as you'd miss some really good nights. Possibly my sharpest Jupiters (
example) were on a night with a 50kt jetstream! I've imaged about
once a week this year, in a range of conditions. Scope cooling and internal fans are definitely important to circulate the air and even out temperature gradients, I leave mine for about 2hr with fans on. I have no issue running the dew control on the corrector, it causes no adverse issues for me (I think because of the air circulation), and that plus the shield stop dew even on the worst winter nights. It's on every night I'm imaging just now.
My general experience seeing-wise, having used a Newt last year and an SCT this year is that I do wonder how much people's consideration of differences comes down to how well the air is circulated in their SCT? After all, seeing is external to the scope, surely?