This is a desolate (ESV) or remote (NIV) place?

ESV, Mk 6:

30 The apostles returned to Jesus and told him all that they had done and taught. 31 And he said to them, “Come away by yourselves to a desolate place and rest a while.” For many were coming and going, and they had no leisure even to eat. 32 And they went away in the boat to a desolate place by themselves. 33 Now many saw them going and recognized them, and they ran there on foot from all the towns and got there ahead of them. 34 When he went ashore he saw a great crowd, and he had compassion on them, because they were like sheep without a shepherd. And he began to teach them many things. 35 And when it grew late, his disciples came to him and said, “This is a desolate place, and the hour is now late.

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Strong's Greek: 2048. ἔρημος (erémos) — 48 Occurrences

G2048 had several nuances. BDAG: ① as adj. pert. to being in a state of isolation, isolated, desolate, deserted
ⓐ of an area isolated, unfrequented, abandoned, empty, desolate
ⓑ of pers. desolate, deserted … a childless woman
② an uninhabited region or locality, desert, grassland, wilderness (in contrast to cultivated and inhabited country)

Compared to ESV, NIV took more translation liberty:

30 The apostles gathered around Jesus and reported to him all they had done and taught. 31 Then, because so many people were coming and going that they did not even have a chance to eat, he said to them, “Come with me by yourselves to a quiet place and get some rest.”

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Jesus wanted to get away from the noisy crowd.

32 So they went away by themselves in a boat to a solitary place.

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The NIV translators didn't want to repeat the word "quiet," so they used "solitary" as a synonym.

33 But many who saw them leaving recognized them and ran on foot from all the towns and got there ahead of them. 34 When Jesus landed and saw a large crowd, he had compassion on them, because they were like sheep without a shepherd. So he began teaching them many things.

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Jesus could get away from the crowd.

35 By this time it was late in the day, so his disciples came to him. “This is a remote place,” they said, “and it’s already very late. 36 Send the people away so that they can go to the surrounding countryside and villages and buy themselves something to eat.”

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NIV used the word "remote" to give a sense of isolation of distance from other inhabited places.

Which version is better?

Both are fine. ESV used the word-for-word approach, while NIV used the thought-for-thought approach. It's up to your preference.