I cannot for certain say a hydrofarm will solve your problems. It might, when you have conditions that cause one on/off to swing another brand that works in a similar fashion may swing as well. If I was to offer one that I KNOW will solve the swing issue I'd have to say a purpose built porportional T-stat like a herpstat, helix, VE, ecozone, herpkeeper, or habistat.

I do not own one yet I have ordered one to test out of curiosity. I have emailed with Nicholas Rossi one of the tech support guys at hydrofarm and was told that the probe accuracy is +/-3% of the set point. "Very accurate for seedlings" I don't think that just under +/-3ºF is very accurate and that is the new improved accuracy version...

A hydrofarm may solve all your issues it may not as well. I cannot say I know a herpstat or the others will however. Just a word of caution.