I think you should try both apps first if you can. They are both very capable and both have advantages and disadvantages when compared to each other.
Also, I think that your iPad being 16 bit has nothing to do with audio recording, you can still record 24 bit audio.
Also, if the price is an issue, keep an eye out for special offers, Auria was on sale for $25 just last week, and Cubasis sometimes also goes down in price, I think I got it for $30.