There's an important difference. AFAIK 'time' is not a program, but a shell command. It prints to STDERR, so you can't capture it with a plain '>' redirection, but even a '2>' won't do, since you have to capture the output of the whole pipeline:

$ time perl -le 'print "foo"; sleep 1' >/dev/null

real    0m1.017s
user    0m0.003s
sys     0m0.002s
$ time perl -le 'print "foo"; sleep 1' 2>/dev/null
foo

real    0m1.012s
user    0m0.003s
sys     0m0.004s
$ (time perl -le 'print "foo"; sleep 1') >/dev/null

real    0m1.012s
user    0m0.002s
sys     0m0.004s
$ (time perl -le 'print "foo"; sleep 1') 2>/dev/null
foo
$ { time perl -le 'print "foo"; sleep 1'; } 2>/dev/null
foo
[download]