Nameless Puppet was definitely harder than Isshin, in my opinion.
Isshin was tough but very fairly designed. Part of NP’s moveset in Phase 2 is a bit gimmicky and hard to dodge/block, which is a bit of a pain.
I think Isshin is easier only in that it’s a better designed fight that rewards you more for learning his moves and tells.
Yeah, I recently bought the GL-MT6000 and it’s been great.