My brother works for a UK based company in INdia. They have an office in US too. Now my brother needs to come to US for 3-4 months to work on a project. He will be working at a client site doing some programming work. Which visa should he go for? B1 or L1?

I heard L1 is easier to get but is it Ok if he is not working in his own company's office and rather working at a client site?

How long is the duration of B1? Is it only for 3 months or you can get for an year too?

BTW He has to apply to the Mumbai consulate.

Any help would be great . Thanks.