Comp XE270S experiences?

The Comp “270S”(part number 20-246-4) is not part of the XE, or in the case of solid cams, “XS” family.
It uses the older Magnum solid lobes.

It would be fine in your application, but you’d probably be leaving a little power on the table compared to the XS equivalent.

A [email protected] cam using lobes from the XS family would have to be a custom.
The smallest XS shelf cam they offer for a SBM is 230/[email protected].

You're right...but it can be argued that no matter what cam he chooses, he's leaving power on the table, as there really is no "perfect" choice. That 270s has slow ramps compared to modern stuff and will be dead nuts reliable, not beat the snot out of the valve train and last forever.