Mizuno makes the best Judo gis. Dax and Fuji make great lower priced gis. HCK also makes a Judo gi but the best is Mizuno. www.SSFgear.com
Kusakura are far the best Mizuno and Mitsuboshi are excellent too I heard that also Toraki are very good too
The jackets are made differently and the trousers on BJJ gis are usually reinforced in places whereas judo gis are not. Also judo gis I have seen have somewhat of a "shoulder cuff" if that makes any sense.
I use a Mizuno Judo Gi, and I would highly recomend it to anyone. It is also good in JJ class, real high quality.
Kusakura are awesome if you can get hands on one. Mizuno are also excellent. Both brands can get very expensive.