As requested:
Could you elaborate on this?
Don't say I didn't warn you...
Main definition:
Nuevo tango, to me, is fundamentally a non-progressive dance. You and your partner are moving around in a (stationary) circle. Most of the (few) nuevo movements I know implicitly recognise that assumption.
Traditional tango, to me, is fundamentally a progressive dance. The leader steps forward, the follower steps back. Everything else is decoration. It's quite conceivable that you could have a lovely traditional tango, walking a mile along in a straight line.
It's possible to dance progressive nuevo tango, but it feels strange. I'm not sure it's possible to dance non-progressive traditional tango.
I also suspect this is one reason why nuevo and trad dancing in the same milonga causes friction. Nuevo dancers naturally want to pivot, trad dancers naturally want to walk. The two aims are difficult to reconcile.
Sub-definition 1: Musicality
I'd also say that achieving good levels of musicality in nuevo seems to me to be harder than in traditional.
This may be because the traditional components can be chopped into far smaller (quicker) components than the nuevo components; it's not a good idea to rush a volcada, for example, but it's easier to change tempo in traditional.
Or it may be because the type of people who do nuevo are more focussed on getting the moves looking good, than on achieving a connection with their partner through the music. Or it may be a reflection of the sequence-based teaching many nuevo teachers seem to love.
Or it may be a combination of factors.
On the music front, I'd also say that nuevo feels better to non-traditional music; some of the movements can't really be rushed, and so if you try dancing nuevo to traditional music, it's bound to look less musical.
Sub-definition 2: Embrace
I'd say that nuevo does not
mandate an open embrace, but that it often looks and feels better in open; you have more space to play with, you get more leverage for the fun stuff, and it looks more dramatic.
Conversely, I'd say that traditional does not
mandate a close embrace, but that it feels and looks better in close; it's easier to establish a connection, and to move "as one", when you're in close.
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Whew...