Ipinjoy - I think you should interview @ UC Davis for sure! These are NOT competitors....UC Davis is a university medical teaching institution. Kaiser is an HMO - they do not share patients at all. You will receive entirely different exposure from both sites. I would be upfront and decide upon what you want from your job opportunities. Do you want to work into a full time job? Either one will do that - CA jobs often start folks at a part-time situation and if they like them will interim them into more hours &/or full time. Kaiser has a real hierachary - it will take you forever to get days & few holidays.
Do you want to go on to something besides pharmacy clerk? If so, a recommendation from UC Davis will carry more weight, IMO than Kaiser.
Do you want exposure to other health professions - both are equal.
No - for an 8hr gig @ Kaiser, no one will blink an eye at UC Davis - as long as you can accomodate your schedule with both, neither will care.