Hi,
I keep bantams and all mine like to tough it out in the snow and rain. If you have a sheltered spot and some shrubs or conifers they will be able to get out of any bad weather. With smaller birds you can keep a few more in the same space though the bantams that I keep ( croads, sussex, plymouth rock, wyandotte) are not as tiny as the true bantams so the eggs are a good size for the size of the birds. They dont scrat up the grass and are cheaper to feed.
The plastic coops like the egloos are reportedly easy to clean out and make it difficult for red mite to hide but wood coops seem to be most popular with many poultry keepers. Coops vary in price and design but in the end its personal choice. A few things to bear in mind are,
coops which are up off the floor prevent vermin from living under them,
external nest boxes make egg collection easy,
second hand coops may be infested with red mite,
coops which have slide out trays, open roofs, access doors removable perches etc are easier to clean,
coops should be water tight, draft free and well ventilated,
covered runs prevent soggy ground and resist contamination from wild birds,
If you buy a coop complete with run, check that the run has the same capacity as the coop - many do not
Buffy
C