There is practically no difference between the two. Your benchmark is flawed, here is a correction (only the addition of delete $INC{'CGI.pm'}; is required):

use Benchmark 'cmpthese';
use CGI();
undef %CGI::;
delete $INC{'CGI.pm'};

cmpthese(
shift,
{
    use => sub {
        eval "use CGI();";
        undef %CGI::;
        delete $INC{'CGI.pm'};
        return ();
    },
    require => sub {
        eval "require CGI;";
        undef %CGI::;
        delete $INC{'CGI.pm'};
        return ();
    },
});
__END__

$$ perl eval.use.v.eval.require.pl  -3
Benchmark: running require, use, each for at least 3 CPU seconds...
   require:  3 wallclock secs ( 3.09 usr +  0.13 sys =  3.22 CPU) @ 37
+.28/s (n=120)
       use:  3 wallclock secs ( 3.06 usr +  0.17 sys =  3.23 CPU) @ 37
+.11/s (n=120)
          Rate     use require
use     37.1/s      --     -0%
require 37.3/s      0%      --

$$ perl eval.use.v.eval.require.pl  -5
Benchmark: running require, use, each for at least 5 CPU seconds...
   require:  5 wallclock secs ( 5.14 usr +  0.14 sys =  5.28 CPU) @ 37
+.31/s (n=197)
       use:  5 wallclock secs ( 5.05 usr +  0.25 sys =  5.30 CPU) @ 37
+.19/s (n=197)
          Rate     use require
use     37.2/s      --     -0%
require 37.3/s      0%      --

$$ perl eval.use.v.eval.require.pl  50
Benchmark: timing 50 iterations of require, use...
   require:  1 wallclock secs ( 1.30 usr +  0.03 sys =  1.33 CPU) @ 37
+.65/s (n=50)
       use:  1 wallclock secs ( 1.31 usr +  0.03 sys =  1.34 CPU) @ 37
+.23/s (n=50)
          Rate     use require
use     37.2/s      --     -1%
require 37.7/s      1%      --

$$ perl eval.use.v.eval.require.pl  100
Benchmark: timing 100 iterations of require, use...
   require:  3 wallclock secs ( 2.61 usr +  0.06 sys =  2.67 CPU) @ 37
+.41/s (n=100)
       use:  2 wallclock secs ( 2.63 usr +  0.05 sys =  2.67 CPU) @ 37
+.43/s (n=100)
          Rate require     use
require 37.4/s      --     -0%
use     37.4/s      0%      --

$$
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