I have a Freshette but I don't have the Whiz, but I have a similar one (squishy material and size).
In my opinion, it depends on what you're wearing. The squishy one isn't suitable for snug pants as it squishes and is harder to feel when a seal has been made with your crotch whereas with a rigid one, it's more easily felt. Also, it takes a bit more time to position within snug pants (not good when trying to P[ee] (this site won't let me use the full "offensive" word that children use) quickly to avoid being caught!) and might force you to have to pull your pants down a bit. A squishy one is better for looser clothing like skirts or [baggier] pants.
A rigid one is easy to just quickly jamb down there and P[ee] without worrying.
I've had more dribbles with my squishy 'P[ee] thing' than my rigid one. In my opinion, the ONLY good thing about the squishy one is that it's compact. The only problem I've had with my Freshette is that because it's in two parts, I've been in a rush and the tube wasn't properly sitting so I dribbled on myself a couple of times.
I strongly recommend a rigid device.
answered 1 year, 11 months ago
Both are great. I think in the end it will come down to personal preference.
Personally, I prefer the Whiz, because it is flexible and easy to squish or roll to put in my pack. (The Freshette is rigid plastic so doesn't compact as nicely)
You do need to be a bit more careful to get a good seal when using it than with the Freshette, ... but it's not hard.