Both Broadway and the West End are world-class commercial theatre districts. They look similar to a visitor, but the way they are run differs in ways that matter once you start booking.
1. Geography
The West End is more spread out than Broadway. Most major theatres sit between Covent Garden and Piccadilly Circus, but Drury Lane, the Old Vic, the Bridge and the Royal Court are notably further out.
2. Number of venues
The West End has roughly forty commercial theatres. Broadway has around forty-one. They are similar in scale; the difference is that the West End has a much larger subsidised sector around it (the National Theatre, the Royal Court, the Bridge, the Almeida, Sadler's Wells, the Donmar) producing work that often transfers in.
3. Prices
West End top prices are usually lower than Broadway top prices. The cheapest seats are also cheaper - a £20 ticket exists in the upper levels of most major West End theatres. Broadway equivalents tend to start nearer $50.
4. Show length
Broadway musicals are typically two hours twenty to two hours forty. West End productions trend slightly longer.
5. Intervals
The West End uses 'interval'. Broadway uses 'intermission'. Both are around fifteen minutes. London theatres now allow most drinks into the auditorium in plastic cups; Broadway has moved this way too but not universally.
6. Booking windows
West End productions tend to book in twelve-week blocks. Broadway shows typically book a few weeks ahead, with closing-notice runs released later. If you are planning a London trip, book earlier than you would in New York.