IS-IS or OSPF as BGP IGP

All, Does anyone have any information on redistributing BGP traffic into OSPF versus ISIS? What about just carrying IBGP sessions? My OSPF database is growing, and I'd rather not carry LSAs with BGP routes as well as private routes, etc. Too messy. By introducing ISIS and using it only as a BGP IGP, what can I expect? Experiences with Cisco gear preffered. -Christian