First thing that comes to mind is the number of images allowed on clariion vs. DMX. Generally speaking a clariion will have a lower number of images allowed. You will have to look up the numbers but it is significant. This would then follow that your production requirements would be larger on the DMX side. Replication would follow what the prod requirements are so use your prod requirements to make the determination as to which platform.

MirrorView/Async on Clariion uses/needs Reserved luns which you have to create and assign to the reserved lun pool. You will need these Reserved Luns on the source aswel as on the targetbox. The size of the reserved luns depends on the size of the several sourceluns to be mirrored. EMC manuals give a formula on how to determine the mostright size to use. Anyway, you will not only need diskspace for the source and the targetlun but also for the reserved luns. It is recommended to create one size of reserverd luns as the Clariion decides with lun in the reserved lun pool it will use next. You don't have any influence on that.
Another main difference is that MV/A underneath works with Snapview.