Of course ultimately, it is about preference and what you value, but just for discussion/fun's sake, let's do this.
Who is a better in this scenario, assuming they both have the same ROI, drawdown, win rate and whatever statistics (lot size) you deem to be important-Trader A: the trader that trades the same few pairs over and over or Trader B: the trader that is able to trade many different pairs?
Trader A is obviously skilled in the sense that he is able to capture the trend moves, counter-trend moves, all the small and big moves in that same few pairs. On the other hand, Trader B is able to understand and execute across different pairs.
Who, in your opinion, is the better trader, assuming you got to pick one.
In general I would say trader B. I say this because there are times when pairs will go dead; there will be very low volatility (or maybe the reverse - volatility is too high to trade). In that sense, trader A would be sitting on their hands while trader B would still be able to trade.
I would also say that if a trading strategy or system is truly robust then it will work across many assets and markets. So if trader A is successfully trading, say, the USD majors, they could likely apply that same strategy or system in other pairs.
If the nubers are the same ... they both have the same ROI, drawdown, win rate and whatever statistics (lot size) you deem to be important ... None of them is better as it is not important if they trade one or more pairs. Howgh