Charters normally fly non-stop from LGW and MAN which is a big plus. First Choice product is good with adequate legroom and IFE. Emirates is OK too but connecting time at Dubai, particularly on the return leg may be awkward depending on the day of the week you choose. Also if on a seaplane transfer they only operate in daylight which could mean extra cost at the Male airport hotel if Emirates return timings don't match. Sri Lankan operate non-stop from LHR but return is via Columbo.