The Gen5 AE and a 2011 (Gen4) TC are identical as far as the airport side is concerned. The only major difference then is the hard disk in the TC. Wireless network will be pretty well identical as will routing ability.
Data storage?? I really am not sure what you are after so it is hard to say if TC is a good idea or not.
If you want something for Time Machine backups then TC is really the best. The Gen5 AE with a USB drive is not reliable for TM. Although some people have used it and had no issues others are less than thrilled.
See http://pondini.org/TM/Airport.html
As just a data store a USB drive.. (you can get 3TB or 4TB drives like Touro fairly cheap), plugged into the AE can be a reasonable option, albeit it is slow. If you are accessing the data over wireless that is probably not such a big hurdle but over ethernet it is slow.
The WD MyCloud is very popular. And rates very well on one of the few sites that have reviews worth reading.
http://www.smallnetbuilder.com/nas/nas-reviews/32244-wd-my-cloud-reviewed?showal l=&start=5
How well it actually works on Mac, sorry I cannot really comment.
Look for real world user reviews.. http://www.amazon.com/Cloud-3TB-Personal-Storage-WDBCTL0030HWT-NESN/product-revi ews/B00EVVGAC6?pageNumber=2
There is at least one Apple guy pretty upset there.
Apple change things so a unit that supports TM up to Mountain Lion may fail on Mavericks.
You may need to wait for a firmware update to fix it.
What do you believe my best options is?
Go with the 2011 Time Capsule and use it for data only or both network and data
Go with the My Cloud
Invest in the new time capsule and use it for both data storage and network
For just data storage the MyCloud does have benefits.. if it can backup its hard disk properly to a USB3 drive that would be great.
A new or old TC, is more designed for TM target backup than data.. network wise there is no big advantage for buying the AC model unless you start to buy AC model computer or devices.
Beyond that you will need to decide yourself.
