What Microsoft classifies as IO intensive I am not so sure, personally I have not seen any sort of IOPS figure(s) for what we could expect from each service tier, it’s not like I can just run DiskSpeed and find out. Maybe the underlying storage for Premium RS databases is more geared to work with complex analytical queries, unfortunately I do not have the funds in my Azure account to start playing around with tests for Premium vs. Premium RS (I would love to).
Also and just as important, Premium RS databases run with fewer redundant copies than Premium or Standard databases, so if you get a service failure you may need to recover your database from a backup with up to a 5-minute lag. If you can tolerate 5 minute data loss and you are happy with a reduced number of redundant copies of your database then this is a serious option for you because the price is very different.
It’s a lot less expensive (just under 1/3 the cost of Premium in Arun’s example), so it could be worth checking out.