No disagreement that an SSD is much faster than an HDD.
The only point of discussion is whether the extra performance is worth the extra cost. Or whether, given a certain cost, if you’d prefer to pay for more speed or more capacity.
The time to make a TM backup doesn’t really matter to me, because it happens in the background. The time to restore a system is important, but you need to factor how often this is likely to happen. For me, I’ve only needed to restore a backup (to recover a dead system) once in 20 years. And I used TM backups with migration assistant twice during that time. I use TM to restore individual files (usually not more than 2-3 weeks old) more often, but I don’t think high performance is needed for that usage.
But your usage patterns and your budget are not going to be the same as mine.