Should labels in forms follow the same grammar rules as titles

http://grammar.yourdictionary.com/capitalization/rules-for-capitalization-in-titles.html

At the company I work at, we follow certain rules for capitalization in titles.
But currently, we're having a discussion whether these rules also apply to labels above input fields in forms.

First name - or - First Name
Last name - or - Last Name
Arrival date - or - Arrival Date
Departure date - or - Departure Date

Opinions are divided and I can't find any articles or grammar rules to rule in favour of one opinion or the other.

I also can't fall back on convention when looking at what other big players do.
Amazon doesn't treat labels as titles and only capitalizes the first word. BestBuy does treat labels as titles and implements the grammar rules linked above.
In the quick search I did, I've seen more companies that don't treat labels as titles than companies that do treat label as titles. But the difference is not that significant to finalize our discussion.

I know the grammar rules mentioned above are more like guidelines, and since it isn't about some important report where the right grammar really matters. Any rule, guideline or strong argument in favour of one of the options is helpful.

So... does anybody know of any rule or guideline. Or have a strong argument that could push us passed this tedious discussion?