I boot my Pi4 from USB but I use a conventional 2,5" harddrive.
This is much more reliable and faster than using SD-cards.
My experience is that normal harddrives live much longer that SD-cards and SSD-drives.
SSD drives are based on the same technology than SD-cards, go figure.
I haven't used an SSD on my Pi4, but my overall experience with SD-cards and SSD drives is not that good.
Ok, SSD drives are fast and use less energy, but just like SD-cards their lifetime is limited versus that of physical hard-drives.
If you do a lot of writing then SD-cards and SSD-drives will not live that long. ( for example, compiling programs with a swap on will definitely age the SSD faster )
Three of my 128GB SD-cards didn't live longer that 7 months or so, go figure !
The backdraw of physical harddrives are mostly the energy consumption.
My PI4 can supply my 2,5" over the USB without an external powersupply but, besides the mouse and keyboard, you can't connect other hungry devices anymore.
Using harddrives with external power should fix this problem though.
And remember, you have to have a good PI4 power supply or you get trouble also !
The official PI4 power supply is 5.1 V and 3.0 A !!!