Dell have a
1GB Ultra II for USD 79 until tomorrow. It is not a bad price.
You already have an Ultra II so you know that it is a sweet, sweet card.
PDAs can not utilize its speed but some cameras and especially card readers can. If you plan to ever exchange SD cards, buy for the future. If you are sure that you will only ever use the card in the Axim, take the savings and go with the cheap vanilla SanDisk.
Then again, some cards do not seem to harmonize well with some devices. My supposedly 66x Ridata 1GB SD performs OK in card readers or digital cameras but sucks in the x50v. My Ultra II and Extreme III cards both perform well.
I'd rather not go for a vanilla (blue) SanDisk.