i think the 360 core is better...
we just had a batch of 9800pros built by MSI at work and they have extremely fast ram and are automatically detected as 9800XTs by windows - Then its just a matter of upping the core and ram to 9800XT speeds and voila
EDIT: MSI confirmed that they were build using the R360 core since the R350 will no longer be produced
the only difference is that they are 128MB parts as opposed to the 256MB in the XT
to test we picked a couple of them at random and booted them up, plonked the core and mem up and relax no problems
the heatsink on them isnt the cheap-shit ATi stock cooler and is quieter and MUCH bigger, in fact even under load it was warm to the touch only so the owners of these cards probably have some serious overclocking potential...... using stock cooling etc
convenient innit?