Why does my Xanax white bar taste different than big blue football which is the one milligram?

Hi. To start you're not supposed to "taste" it... You're supposed to swollow the pills.
With that being said, there are many different manufacturers of the generic Xanax pills. Are you comparing apples to apples? If both pill in question are from the same manufacturer then chances are they should "taste" the same. However, a generic manufacturing process has the same "active" ingredients that the brand name manufacturer, BUT, those manufacturers use different "fillers and or binders" in their brand of Xanax. Meaning: the active ingredient in the name brand is a propiotory process and other manufacturers use different "inactive ingredients" to make their products different. Most of the time these "other ingredients" do NOT effect the way that the medicine works. However, these "other" ingredients, including binders and fillers, sometimes effect the way the active ingredient is delivered and distributed within your own bodies bloodstream and organs. This is a concern for some people and their health care providers if the expected results are different than normal. Hence the reason that the doctor may write-on the prescription "brand necessary".
To get back to YOUR question, check the brand names on the two different doses of Xanax. It could even be a different "taste" within the same manufacturer if the doses vary substantially, as in your case, because the higher dose and subsequently larger pill size might lead the manufacturer to add more of the same fillers to achieve the larger pill size. I know, these seems complicated but it's a fact in most cases.
Be sure that whatever you are "tasting" or using is personally obtained by you from a reputable pharmacy.

Best Regards,
Kevinb1953