Confused, should I buy a tablet or a mobiel phone for internet related tasks

hello eti I'm was planing to buy a new device next week but im confused which one to buy.. mobile or tablet.
my is based on internet, i use use emails/dropbox, and other services. I know a tablet would be easier but on the other hand I don't have a good phone right now. I am using nokia s40 cell phone since last 3 years.

Should I go for a tab or a good mobile phone ? My budget is around 15k. please give me you advice .thank you.

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