and does anybody know if the Series 1 can be bought with wooden interior design and leather seats(probably the exclusive version) ?

It's all personal preferance... Basically it should come down to what you expect in a car... the BMW 3 series has been around forever, and have built quite a good reputation in their time, while the 1 series is new. I wouldn't be to worried about the 1 series being any less reliable than your average BMW, they tend to make great cars year in and year out, regardless of the series.

yes you can get in coustum made

No reason, except the 1 series is easier to park since it is smaller.