Mmmmm...So I see AR are back at LHR. The Argentina-UK routes are the ones I take twice a year; at the moment, with BA.
If AR offer cheaper fares than BA to EZE (BA's fares are pretty competitive, excluding Club World and First, which are a rip-off), then they may get good load factors, and good luck to them.
However, my parents expect very good service AND reliability, which they get every time with BA. Let's face it, they're a great airline worldwide. We did try AR once, via Orly, (747SP as a matter of fact-it was leased).
The service was not impressive. The PA system broke down, the IFE (main sceen) broke down 5 hours into the flight, and the FA's were rude.
That was enough; adios AR, hello BA. And we've never changed, they're absolutely fabulous, and always on-time. The BA FA's are mostly Argentine, or Latinas, so it's not that Argentine FA's are rude, they just need good training (BA-say no more).
Everyone I know here flies BA to Latin America. Another fact. Guess what airline the Argentine ambassador to the UK flies home on. You've guessed it, BA (and they upgrade him from Club to First, well they should really).
SO, thanks AR, but no thanks. We're sticking to BA.
Why on earth is an airline on the verge of bankruptcy inaugarating new international routes? Madness!