well i think in both cases the speed of development would remain almost the same, might even be a little faster for weekly updates due to constant pressure to meet deadlines.....
but as they say "there's a downside to every good thing"
the weekly updates may lead to a rather rushed game with the creator not being able to bring out all his imagination and is bound by the constrains of time....
(the above statement is true for almost all games but i'll rather make an exception for this game as Archadian has done a great job of cooping with the stress and developing the game to its full extent.)
(IN SHORT WEEKLY UPDATES ARE BETTER IN CASE OF THIS GAME)
hope u got ur answer, kudos