god i hope so there ikarus.
i do both, friendly games are fun cuz it allows you to bring those units that you just had to have the models but aren't truelly that great (tyranid biovore, for example). plus it's fun to try out different tatics, i set litte goals for myself. like play to the fluff, berzers don't care if there are genestealers in front of them they'll charge, and die. but that's one way to enjoy your game set a goofy goal for a unit and do it regardless if tatically it may be a little, well stupid. i belive you should shot a demolisher round into a squad that is mere inches from other friendly and enemy units. cuz lets be honest on the battle field the carnifex is getting shot with everything regardless if the round may kill a few guardsmen
but i will agree with ikarus if you have power gamer just out power him, come up with a cheesier list, before you know it you be on a mountain of spagetti setting on a meatball.
so i guess my advice is don't take the games to serious, yes it's nice to win but it's the experience you get by enjoying a game with a like minded person. it's only 4-5 hours that your wife well ***** about anyway.