I trade 24 and if you're doing those amount of pairs it's not usually predictive trading. So the questions is more or less irrelevant. You'll only do it to win, but not by pair. By portfolio.
Anything with a spread less than 7 pips, I think was my criteria...
EURNZD is a particular pain in the arse. Just borderline spread wise.
And in that I would trade EURGBP against both EURUSD and GBPUSD which makes no sense at all in conventional FX thinking...it's either doubling up my position or hedging it. There will be similar examples in the rest of the pairs.