You didn't mention what price range and learning curve you were looking for. When I did my search for synths the 2 that popped out at the top for me were Alchemy
. I finally ended up buying Omnisphere and it does have an extremely powerful and flexible arp (and also quite a big learning curve if you want to go beyond the presets and libraries).
However if you dig into the synths you got with Mixcraft you will find several good arps (I can't remember which offhand: OFC) AND there are also dozens of freebies available that offer arps.