I'll just throw in a bean counter's perspective here, which usually gets a rather heavy weighing when making aircraft purchase / lease decisions. It is not common knowledge, but when it comes to the cost of an engine, over the lifetime of the engne one usually pays 1.5-2x the original purchase price on shop visits. Since the cost / power is non-linear, bigger engines cost less per unit of thrust then smaller ones (logical, the material cost may be less - and for the exoic alloys used it is not negligible - however design and assembly costs are close to being the same, regardless of big or small). Multiply that by the maintenance factor, and over the lifetime of an aircraft even if fuel consumption is similar, four holes will cost much more than two.
About a decade ago I had the opportunity of comparing Avro RJ100 / Fokker 100 for an interim lease of nine months. The two aircraft were roughly the same hours/cycles the Fokker was offered at a monthly lease rate of ~$55k. We did the maths and found that all other things being equal the lessor of the Avro would have had to give us the aircraft for free to compensate for the difference in maintenance reserves (roughly 25k per engine).