These are listed in the order of my priority...
Days to maturity
The shorter the time to maturity, my better chances of having a harvest before disease and insects.
Disease resistance
The more resistant, the less I have to spray.
Insect resistance
The more resistant, the less I have to spray.
Tender and Flavorful
Taste is important too. Even if it grows fast and is free of insects and disease, if we don't like it, we won't eat it.
Non-hybrid AKA F1
Saving seed is important, but not at the top of the list. Hybrids often offer more disease and insect resistance.
Easy to grow in pots
Cabbage family not included since they grow well in the ground here in the fall, winter, and early spring.
Will grow in short days of winter
Some plants just won't grow with our short days of winter. Garlic and long day onions coming to mind first.
Price
Question whether it is worth buying more seed and saving it versus buying smaller packets.
I am again buying my seeds from Twilley. Great prices and resistant varieties. Request their catalog here: http://www.twilleyseed.com/Request_New_Catalog.html