IN or EXISTS?? faster one

Hello All,

I am using too many subqueries in my queries. I have read some
FAQs that using EXISTS is faster than IN. Is that correct?? I
tried to get the total runtime using EXPLAIN ANALYZE, but i got
total runtime for the query with IN but not for the query with
EXISTS.

query with IN:

EXPLAIN ANALYZE Select * from bom where depot_id in ( SELECT
depot_id from depot where company_name ='SOME' );

query with EXISTS:
EXPLAIN ANALYZE  Select * from bom WHERE EXISTS ( SELECT depot_id
 from depot where company_name ='SOME' and depot.depot_id =
bom.depot_id );

I read the same for using with select count(*)...is too slow. How
to replace for that??

Moreover, what are the other things one should take care of
regarding reducing the time taken by the queries??

Thanks in advance.
Regards
Prachi