According to B::Deparse, they seem to be treated the same (Tip #6 from the Basic debugging checklist):

$ perl -MO=Deparse -MDateTime -e 'DateTime->now'
use DateTime;
'DateTime'->now;
-e syntax OK

$ perl -MO=Deparse -MDateTime -e 'DateTime->now()'
use DateTime;
'DateTime'->now;
-e syntax OK
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