SSD is now the best
I have switched boot drives on the devices I use all the time to SSDs. I did this solely on the basis of dramatically better performance. That is, my prejudice was in favor of traditional HDDs, but SSDs were so much better that it overcame both the price per GB advantage and my reluctance to embrace the unknown.
My systems have always been on a pretty extreme budget, so swapping out boot drives was only done because the advantage was so compelling.
For me, performance differences are always less noticeable upgrading than downgrading. The upgrade was dramatic and at this point I expect the downgrade would have me wondering if the machine is failing.
If you have any latitude at all and are booting or doing anything read/write intensive from HDDs, I suggest you give SSDs a try.