I think the general consensus when it comes to best era Napalm Death lays with either "Scum" or this, their second LP from 1988 "From Enslavement To Obliteration". Personally, this one's my pick, and here it is. Earache #8, black vinyl. Secured via eBay for a modest buy it now price. So much influence was spawned with this album, just about every great modern grind band would openly admit to taking direct influence from this album in particular. You just can't argue it at all.
Obviously Scum more or less spawned grindcore, but this LP cemented the genre indefinitely, and truly displayed the band firmly settling on an idea and an approach, even if they did progress on from this style pretty quickly with the following material. One could argue that with 'Enslavement, Harris certainly hit his peak in the drumming department, the centre piece that undeniably powered the band. The recording here is obviously cleaner too, more succinct, and more together, a luxury that was afforded to the band with the Earache deal.