Spiraea vanhouttei vs Spiraea arguta

I've bought both, over the years, presumably both still alive, no idea which is which, how do I tell the difference between them?

 

Never grown either myself.
But had a quick look on Google and they look very similar.

 

Best answer so far (Just trying to break a record for "Agree" rating )

 

Post chaser?

 

I have both too. With me the Arguta flowers earlier and is more delicate. I prefer Arguta but both a good reliable shrubs. I try hard to always prune Arguta after flowering Vanhouttei doesn't seem to need pruning as much but that's only my opinion.

 

Snot working !!

Probably a bit late for me to check that ... but I'll go out and have a look, thanks