In particular, on cello. I got the impression that both are strong (either by pressure or speed) at the beginning of the note, followed by quick release of pressure/speed. What is the difference between the two?
I assume you mean the difference between ^ and >. Both signs are used as accents in generally. The correct designations are marcato (>) and martellato (^).
Usually marcato means accentuated and martellato means strong accentuated. So you see that there is only a small difference. And it is often discussed how exactly these two accents are played differently and in particular with a certain instrument (like in your case a cello).
However sforzato and/or sforzando (sf and sfz) are dynamics. They are dynamics and mean with sudden emphasis in the sense of sudden change of the volume.
So summarizing: accents like ^ and > are similar to dynamic instructions like sforzando and sforzato, but they are not the same.
2I wouldn't treat any accent mark as "sforzando," seeing as sfz is written in the score when it's wanted. (or sf, or sz). Feb 20, 2019 at 13:05
@CarlWitthoft Thank you for the hint. You are right. I changed my answer.– IQVFeb 20, 2019 at 13:19
A sforzando(sfz) is the loudest and strongest accent. It is not really considered a dynamic as another answer suggests.