It looks to me like both midori and netsurf are "heavier" than either firefox or chromium, if heaviness is measured in run dependencies.
Code:
$ cd /usr/ports/www/midori
$ make full-run-depends | wc
89 89 1491
$ cd ../mozilla-firefox
$ make full-run-depends | wc
42 42 696
$ cd ../chromium/
$ make full-run-depends | wc
57 57 948
$ cd ../dillo
$ make full-run-depends | wc
16 16 237
$ cd ../netsurf/
$ make full-run-depends | wc
64 76 1185
$