i haven't done any tests to verify this but i guess it should affect the framerate on slow graphic cards.
pick a model that has a low amount of triangles and then use cg_forcemodel "1" to force all the other players/bots to use the same model as you.
here's a list of triangles used in different models for openarena.
the totals are for the three different level of details used for the model, different LoDs are used depending on how far away the model is.
the total amount in the three columns are the added triangles of the head, upper and lower parts of the characters.
i've added the quake 3 models of anarki and biker for reference.
modelname total LoD_1 LoD_2
angelyss 3090 1680 1810
arachna 3510 2670 2080
assassin 1830 1830 1830
ayumi 2325 2325 2325
beret 1800 1800 1800
gargoyle 3130 1820 1060
kyonshi 2530 1920 1180
liz 1900 1900 1900
major 1130 1130 1130
merman 2070 1485 765
penguin 1770 1770 1770
sarge 1530 1070 645
sergei 2565 1910 1440
skelebot 2220 2220 2220
smarine 2550 2550 2550
sorceress 2280 2280 2280
tony 1190 1190 1190
anarki 830 530 300
biker 790 440 280note: "sarge" is the grism character
note: this is just how i've understood how it works - it may not be the world's most accurate study