echo returns nothing. Keep in mind that neither is actually a function, but rather language constructs.
echo allows you to pass multiple strings when using it as if it were a function (e.g.,
echo($var1, $var2, $var3)).
echo can also be shorthanded by using the syntax
<?= $var1; ?> (in place of
<?php echo $var1; ?>).
As far as which is faster, there are many online resources that attempt to answer that question. PHP Benchmark concludes that "[i]n reality the echo and print functions serve the exact purpose and therefore in the backend the exact same code applies. The one small thing to notice is that when using a comma to separate items whilst using the echo function, items run slightly faster."
It will really come down to your preference, since the differences in speed (whatever they actually are) are negligible.