I like RAIL as it's well written but sometimes highly one-sided on some issues (HS-2 especially)
I've read Modern Railways for decades and still get some enjoyment out of it, though recently it has become very technical. (signalling and loops and other such stuff)
On my recent visit to the UK I found Rail Express and Today's Railways both for the first time.
Rail Express sems to go for the all-round fan, as it says on it's cover News; Nostalgia, preservation and modelling. Today's Railways seems to be strange as the June issue I picked up was Issue 198 and was Europe Based, and the July Issue was Issue 127 and was UK based. I have enjoyed reading both issues.
As a massive fan of the GWR and who isn't? (I want to hear from no dissenters) - I pick up when in the UK, Great Western Railway Journal. Full of old and ancient GWR stuff.
I subscribe to Modern Railways and RAIL. As there is no decent mail service here in Baku, I have my magazines sent to my home in Bangkok and when I return home every 3-4 months I have a great stack of reading material to wade through as I sit back in my armchair and slowly get through my Duty Free Cognac!
Of the lot I'd go for RAIL. I do enjoy the railways based crossword at the back, as
sometimes I actually can complete it.