Hi Nagaraju.
I think that depends on your skills and what tasks you preffer. Personally I think SAPUI5 / Fiori is closer to what we do as Abapers because is programming. You'll have to learn a little bit of Javascript, HTML5 and CSS3 but I think the learnig curve is better than learning HANA, which I consider that suits better to BI/BO consultans.
Eventhough, HANA is another interesting option, but as Abaper I preffer SAPUI5.
Hope this response be helpful for you.
Regards,
Dairo.