This depends upon the place where you lived or want to work at.
Suppose the place where you are living has many Web development companies, do you think that Data scientist has more chance to get hired than a Web developer and vice versa.
But in general I think Data Scientist is high on demand because data is proving to play a very vital role in our future and the second reason is because number of Web developers is greater than number of data scientist, common sense right!
(But who am I to even comment on this topic, think about it :'))
you should study both
cause even if data scientist market is down, cuz you have to make an app in js, like a social media, you like someone's comment, then you logout, then you log back in, you still see that like, if you want to become more popular, study web devlopment
so study both
Actually my answer is both... Because we need web develop to make websites and web design I guess you know all about that but on the other hand we need data-scientist to write algorithms and backend for websites... What I can tell you is you can find lots of web developers but there are very few data scientist who can write algorithm on server side using their true CS knowledge... So go for DATA SCIENCE, it's unique to have that skill.