You will find both are very similar to each other, especially for common tasks. See: www.openbsd.org/faq/

I have OpenBSD on a R51e and had it on a T61. No issues except sleep and resume. R51e fails, T61 works except on resume you loose your USB ports.

Now NetBSD works great on the T61, no issues. The R51e I kept with OpenBSD.

Also note this quote from OpenBSD: “… only easy and critical security fixes are backported to i386”

www.openbsd.org/i386.html