personly i feel that HB, Las and Las/Plas and assault are the types that can be ran depending on what you want to use it for and your oppoent. Las/Plas is good agian light armoured enemys like Orks, Dark Eldar who normaly have poor armour on most transports etc. Las is great for the heavy stuff like Vindicators, Landraiders etc (anyhting AV12+). Assault is your generic one and personyl i feel the bests as it can do anything (even Pen Landraiders) and the HB's are only there is you can't afford the others.
"Never take life seriously. Nobody gets out alive anyway."
People i have turned into Chaos Spawn