Hi echo,
A forum search on Casper Tuft Needle will bring up all the forum posts that mention both of them them but I would also be aware that these are very different mattresses and aren’t really “apples to apples” comparisons. I would also be aware that warranties aren’t an indication of the useful life of a mattress (see post #174 here).
There are also other options that are available to you in similar budget ranges that may also be well worth considering also that would also be very good quality/value choices.
If you haven’t read it yet I would start with the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and know how to avoid the worst ones. Post #13 here also has more about the most important parts of the “value” of a mattress purchase that can help you make more meaningful comparisons between mattresses.
The end of post #4 here and the posts it links to also include some of the better lower budget online options I’m aware of as well.
Phoenix