The main advantage as far as I'm concerned is semantic integrity. You stil get to think and model in OOP terms. That's valuable and good abstractions are worth

The main advantage as far as I'm concerned is semantic integrity. You stil get to think and model in OOP terms. That's valuable and good abstractions are worth some trade-offs. Of course you also get that if you use an object database like ZODB but you face similar trade-offs most noteably speed which is usually solved by using a RDMS for indexing.