On routes served by more than one carrier, Heathrow to Delhi for example, where British Airways, Virgin Atlantic and Air India all operate directly, service standards, baggage allowances and typical pricing all differ meaningfully. Don't default to whichever airline appears first in a search. Compare at least two before booking, particularly for a long-haul family trip.
Price is the visible difference; the others surface mid-journey. Baggage allowance can vary by an entire suitcase between carriers on the same route. Departure and arrival times matter more than they look. An overnight flight landing in the morning and a daytime flight landing at midnight are very different propositions with children or an onward journey. Meal service, seat configuration and how the airline handles disruption all differ too, and none of it shows in a headline fare comparison.
Five minutes covers it. Pick the two or three carriers on your route, check each one's baggage allowance and arrival time against your plans, then compare fares on equal terms. The route guides on this site list which airlines fly each pairing and what the fare has looked like when we've checked it, useful context for judging whether the price in front of you is normal for the route or genuinely worth moving on.