i am sharing my opinion on the same.Because some say they are both having good capabilities ,some say they hold different startegies and its a comaprision of two different fruits like apples and oranges.
Whats there is technically:
In Hana data is stored in one place and in exalytics data is stored at different places.If we want to report the data on sap-hana we will use one single system.But for exalytics we have to involve with some transformational and loading type operations with the data base.
As i said in the earlier blogs database plays very important role in any application.So for exalytics(i hope) moving the data will takes time and it will not match databases as it store data at different places.(If ess base is one such data base it wil not acept any special symbols..which is bottle neck again) and internally we have to manage many things in moving the data and might be as i observed the space volume will be tight for exalytics when its a thing of processing huge volumes of data,it has only 300GB of actuall memory.
As of Hana we can design the data differntly.We can also work without moving the data also.As a whole system it serves the best to promote the data migration capabilities very effieciently.because HANA data can be imported pretty much continously.Also Hana uses the business functiuon library to enrich various kinds of databae capabilities.Exalytics are using statistical functions to make their analaytical capabilities more strong.