Hi there, I'll try to give you some answers to your questions
West coast location - if you're ON the coast it might not be too bad, but the west is where the midges are !!! Midgies are hellish, they get everywhere - in your ears, eyes, hair etc etc but avon's green skin so soft works a treat for keeping them at bay - as long as you don't mind being 'oiled up'! LOL! East coast doesn't have the same problem. Also west coast always seems wetter than east coast.
The growing season is shorter than down south - you can have late frosts well into May & sometimes beyond, early frosts can happen as early as September - it's just your luck on that particular year. But croping in polytunnels will extend the season.
As for land & livestock - choose your smallholding carefully, check for evidence of flooding and poorly drained land, examine condition of grass/crops growing there and make your judgement as to whether it looks fesible.
And as for why Scotland would be good ?
It's the most beautiful country in the world !!!
Rugged mountains, tartan coloured moorland, dramatic coastlines, clean, fresh air, friendly locals (as long as you're nice to them) makes it a wonderfull place to live !
I'm totally biased, but hope this helps a bit.
I think every area you're looking at will have it's pros and cons - you'll just have to try & get a gut feeling of where's right for you.
Goodluck with your search and do let us know how you get on
Karen