I'm not sure if THE best software exists. It would heavily depend on what you need to do with your NMR data.
For Bruker NMR machines, the Topspin software that is installed on the acquisition PC would be fine for most basic tasks. For third-party software solutions, I think the software packages from Mestrelab and ACD labs are the most widely used. These packages offer functionality beyond what is provided by Topspin. Also, I believe both companies offer solutions for MS and other types of spectroscopy in the same package as well, for all-in-one data processing and interpretation.
Luc is perfectly right. I REALLY depends very much on what you want to do. To add two which is widely used for quantitative NMR based (plant) metabonimcs: https://www.chenomx.com/ or https://spin.ccic.osu.edu/index.php/colmar
... but is definitely is NOT the one if you are after de-novo structure determination of yet unknown natural products (here ACD with all its packages may help, as Luc already pointed out).
Just do mention that Topspin is toally free of charge for acamedia. Meaning you can install a processing version on your private computer too.
MNova has the advantage that you also can analyze other data like MS in addition to NMR. Like it was already mentioned, it is convenien (especially to users new to NMR), but it is noct for free.