You’re right. By and large, they are very similar. The qualitative difference shows up in two ways. One, within the translation itself, and the other when compared to the views of the translator.
Within the translations
He turns his mind away from those phenomena, and having done so, inclines his mind to the property of deathlessness: ‘This is peace, this is exquisite — the resolution of all fabrications; the relinquishment of all acquisitions; the ending of craving; dispassion; cessation; Unbinding.’
They turn their mind away from those things, and apply it to the deathless: ‘This is peaceful; this is sublime—that is, the stilling of all activities, the letting go of all attachments, the ending of craving, fading away, cessation, extinguishment.’
The terms fading away and extinguishment has a connotation of nothing left afterwards. However, the terms dispassion and unbinding, being more clearly linked to the aggregates are more difficult to interpret as nothing left afterwards.
Of course, how this is taken is very individual. But by and large I think it is not as easy to conclude that Nibbana is the same as nothingness with Ajahn Thanissaro’s translation.
With comparison to translator’s opinions
This is probably the more serious issue.
If you have a preference for Ajahn Thanissaro’s teachings and translations, his rendering reads well because he has made clear in his writings that there is consciousness outside the aggregates. Thus there is a mechanism for explaining the experience described in the passage.
If you have a preference for Ven. Sujato’s teachings and translations, his rendering doesn’t read as well because he has made clear in his writings that there is no consciousness outside the aggregates. Thus, there is no mechanism for explaining the experience described in the passage. The translation and the translator’s own views are at odds with each other.