i suppose it is whatever suits you personally, canvassing is a hard thing to do if you arent comfortable with it , i did door to door sales for years and started most of my rounds that way , but now i'd much rather come home in the evening and spend it with my family after working all day - so leaflets work for me,
i have found that by having a good design and dropping in bulk you get a good return... but it costs money, whereas canvassing is free other than some diesel and your own time... and i doubt it's a northern thing look at the results lee pryor got , he is in sussex i think?
I reckon if you need the work quick or like canvassing then yes it is a good way , but if you dont have the time or want a steady trickle of constant work , leaflets work very well with almost no physical effort if you get them delivered , so even the busiest of window cleaners can still be finding more work!
Just a point on area - The area i put mine in during april is probably one of the more competitive areas full of window cleaners in the country , i had more threats than customers ringing , the only reason i put them out in it is becasue it is close to home and i wanted to try get some local work as majority of my work is ten plus mile away -- but to my surprise i still got work... so i dont think that comes into play , it is about how many you drop !
And i have found that those areas which are tied up by ladder cleaners in patches have lots of custies desperate to get away as many offer a crap service and come round to regularly , i have picked up loads who are sick of fortnightly cleans who miss windows etc , they are willing to pay much more for better service monthly (that isnt a slur at all trad cleaners, just the majority

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