Etymology of "choice" — New Zealand vernacular
Solution 1:
Choice is commonly used in BE to mean "of high quality"; butchers, for example, often advertise "choice cuts of meat". See http://dictionary.cambridge.org/dictionary/british/choice_4 .
Solution 2:
The Concise New Partridge Dictionary of Slang and Unconventional English (2007) says its fairly recent:
choice! used for expressing strong approval NEW ZEALAND, 1998
Here's some slightly early examples from Usenet. From 1995:
Hey, another NZer! Choice Bro'...
From a 1996 'Are you are real kiwi test':
- What does 'choice' mean?
a) Excellent...
The Dept of kiwi immigration has but one word to say to you : CHOICE BRO (ok, technically two words but I never could count)
Lonely Planet's New Zealand guide (2010) gives a slang synonym, although as New Zealander David Wallace comments, chur isn't as strong as choice:
choice/chur – fantastic; great
Choice was also US slang with a similar meaning, could they be related? It can be found used by Americans in Usenet in the late 1980s and is defined in American Slang: Cultural Language Guide To Living In The USA (2005):
Choice: very nice; great; awesome. This cigar is choice. Management thinks you are choice for the job.
This is closely related to choice as in a choice cut of meat and choice words, as detailed in other answers.
Solution 3:
I would think it is fairly straight English. Found in expressions like choice morsel.
Solution 4:
The OED defines choice as an adjective as follows: Worthy of being chosen, select, exquisite, of picked quality, of special excellence. This seems to fit your usage. This is a very old word; they have citations for this sense going back to 1370:
1340–70 Alex. & Dind. 727 Him a chalis ful chois wiþ good chere bringen.
It may have fallen out of common usage before being revived as slang (perhaps acquiring new connotations in the process). But it is still around in standard English. For example, here in the U.S., the federal Department of Agriculture assigns quality grades to meat which include Select, Choice, and Prime.
Often, when obscure or obsolete words are revived as slang, they acquire meanings that are very different (radical, cool) or indeed opposite (sick, killer) to their literal meanings. But sometimes the literal meaning is intended (though sometimes exaggerated). The first example I thought of is heinous.
Solution 5:
I agree with Tony Balmforth and would like to add that in OP's context, it is likely akin to sufer slang, although it still means "the best" in this vernacular.
Unfortunately, my copy of Partridge's Concise Dictionary of Slang and Unconventional English has no entry for 'choice'.