Hi hedkikr,
if you want to know more about Seido, you can always check out these websites.
http://www.seido.comhttp://www.seido.org.uk/london.htmThe first website is from Kaicho's dojo in New York. The second one from London, where I study Seido.
I don't have any experience in other MA's or styles. When I joined my dojo, I had just moved to London from another country, so I didn't have a social life or friends in London. people made me feel so welcome, and I made some good friends right from the start. It is not a really big dojo, and there is a lot of friendship there, a good 'family'feeling kind of thing, with lots of nationalities what makes it so intersting. People don't come just only for karate, they come to be with other people with the same interest who are also their friends. I don't know what it is like in other dojos, but this is what I love about Seido karate.