Roth or traditional for the property itself? I keep flipping.

I have both a traditional rollover IRA and a Roth, and enough in each that either one could buy a small single family rental with cash. The custodian doesn't care which I use. I do.

The Roth case is the obvious one. Rent comes in tax free, and when the house sells years later the gain is tax free too, assuming I follow the rules and keep every dollar of income and expense running through the account. If the property does well over twenty years, that compounding never gets taxed. That's the whole reason people bother with this structure.

The traditional case is less romantic and still real. My Roth is smaller. To get the Roth big enough to hold a house comfortably plus reserves, I'd have to convert a chunk and pay tax on the conversion at my current rate, in cash, this year. The traditional account can buy the same house today with no tax event at all. Rent still compounds tax deferred inside it. I pay ordinary income tax on the way out, decades from now, at a rate I can't predict, and I have required distributions to plan around eventually.

So it's a bet on my future tax rate against a real cash cost now. There's also a middle path where each account owns a piece, though then I have two accounts sharing one asset and every expense has to be split by ownership percentage forever, which sounds like a bookkeeping trap.

Anyone who has actually chosen, what tipped it? A conversion of this size is something I'd run past a tax professional before signing anything.