In my opinion (which may mean nothing!) and based on what I have been told at my local club, a .46 is too gruntly for this size hull.
A .32 is the recommended maximum size, considering this size hull is for a .21 anyway.
As for your 2nd option of the .21 looks like its a real goer, though seems a heck a lot of money if you do not intend racing the boat!
If I were you I would do some searching for any feedback on the .21 which is obviously OS's latest and greatest!

I ended up going with the .32 as I wanted the pullstart and had heard a lot of good feedback on t as well as seeing it in action in the same size hull. No doubt everyone has different opinions, thats where ther eis nothing better than to see the setup you are after in action.
By the way the Dynamite .32 where others have suggested in this thread...if I were you I would stay away as it is only a cheap sport motor designed for cheap RTR kits. I use to have one and had majors issues in trying to get it to hold a tune, so ditched it for my currect OS.

Good luck with your decision...I know what its like when you want to buy NOW cause you can't wait to hit that water!! I would be interested to know what sort of speed you get out of your .21!!!!!!!!!