I found the An148 to be a compelling upgrade immediately after building up a regional presence early on as the range itself was compelling enough for me along with the passenger cap and relatively low price. I didn't move to A318 until I was directly competing on large, high capacity routes with other airlines. The lower efficiency and profit initially is offset by the much lower cost of the Il-96-300 which aren't too much affected by higher margin intercontinental flights in my experience. They're kind of like a bootleg version of the 767-600ER for a third of the price. I found out the hard way about the 350+ PAX fee multiplier increase when I tried to go for the 400 seater Il early on.