not many types of breads that are bad for you, but i've heard there are some that have high fructose corn syrup in them in the US some how so i would avoid that all together, other than that there is just more benefits in whole grains really.
a good read on all the good things with potoatoes, this site is non propaganda fueled and non profit with a complete reference list..
http://whfoods.com/genpage.php?tname=foodspice&dbid=48
As for aspartame? i'm sure there are better things you could be eating instead however it remains one of the most tested food additives ever and there has yet to be any conclusive evidence supporting it causes any harm in anyone... That being said it's also one of the most consumed additives in north america... wouldn't there be some sort of grand scale epidemic if it were that harmful?