Depends a bit what you want to do with the bench and how you will load it. Will it be heavily loaded from the top, will there be movement along its length that might cause legs to wobble.
Edit for example I wouldn’t want to be doing lots of lengthways planing/sanding/hammering/along the grain handsawing on that second bench in the pictures above. It’s a neat design but I reckon it would wobble side to side. The top one looks better in that regard.
I was going to go down this route and decided that actually some saw horses (big Stanley plastic ones) and a 1200×600 piece of OSB edged with some batten and a place to mount a small vice + a cheap workmate copy would give me what I needed for most jobs with very little compromise and portability to work outside on a nice day as well as saving space (as I needed the saw horses and workmate anyway for some stuff).
Horses for courses but even at this time of year if it’s dry I’d much rather be working outside than in.