I have been flying internationally for over 40 years and have been to over 150 countries. Between Argentina and Europe, these are my ratings and commebts about the airline doing these routes at this moment:IN REGULAR ECONOMY CLASS
BAD:
Aerolineas Argentinas CRAP! bad food, surly and indifferent service, flights massively delayed and cancelled
IBERIA: like taking a shuttle service between Madrid and Barcelona, often with YOU SUDACA attitudes(Sudaca is a very derogatory nickname to S Americans!)
AIR EUROPE: only one I have done for a reason of the so many negative comments
PASSABLE:
ALITALIA crowded, screaming kids, screaming adults, indifferent staff, bad "Italian"food, SCUZI NO C'E PIU!(sorry, we dont have any more!)
DECENT:
BRITISH AIRWAYS normally fine, good in flight entertainment, staff varies, LHR awaits you if you are in transit

put your running shoes on!
LUFTHANSA: predictable, alles in ordnung and you VILL like it! very professional
KLM: Friendly, on time, loved their day flight
AIR FRANCE not bad, professional but watch out for the famous GREVES(strikes) you might get out of BA but if you're going further, it can be a hairpulling experience; CDG is horrible for transfers
GOOD:
TURKISH: a great choice but not practical if not going to southern Europe or Middle East, Asia or Africa The way I'd go if I could!
There are also many choices such as TAM, TAP,SWISS,LAN etc which involves normally change of planes in Brazil or Chile
Going via the USA is for the insane as this makes the flight a 2 nighter as well as dealing with US immigration and customs EVEN IF YOU ARE IN DIRECT TRANSIT! Plus, no US airline , sad to say, is good these days and who wants to pay for each glass of wine or other small services offered for free on most other non low cost airlines!
If I could fly Emirates, Qatar, Turkish, Singapore or Thai everywhere, that's where I'd be!
Bon Voyage!