I use the Jacobs exhaust brake on my '03 Dodge/Cummins as it came from Dodge when I bought it new, with a full mfg warranty. Its been flawless in 256k miles.
However if I had a used diesel truck out of warranty I would go with the Pacbrake. It has the same braking performance as my Jacobs at mid to max rpms but the Pacbrake has more braking performance in the lower rpms (1800-2000 rpm). Plus its air pressure activated and comes with its own air pump. The air pump can be used for other things.
Your gonna' like the exhaust brake. In fact I wouldn't own a diesel without some type of exhaust braking system.
'03 Dodge 2500 Cummins HO 3.73 NV5600 Jacobs
'98 3500 DRW 454 4x4 4.10 crew cab
'97 Park Avanue RK 28' 2 slides