Oh, totally - but if the unit has been stolen, and the police actually find it - they won't have the savvy to:

a) figure out what it is
b) find a power adapter to plug it in
c) come close to discovering that is has an ESN in flash ROM

At least with an 'old school' serial engraved into the unit, you stand a better chance of having someone discover that it's stolen, either by the actual number, or by the fact that the punk selling it has scratched it all up trying to eliminate the number!