it would only cost about 70.00 to replace our 30 foot poly cover, God forbid we need to just yet,
I'd go for both if it was me, the green house, this time of year and spring gives you, in my opinion, better light levels ,but you get more space for your money with a poly, ours cost about 380.00 two years ago, for 30' by 10', our 6x8 greenhouse cost us more than that when we bought it, 8 years ago.. :)