Hi Nora! This is a really good question, and the answer is a bit complicated. To start off, Tagalog and Cebuano are not mutually intelligible. Let's compare the two sentences:
ENG: How much is this?
CEB: Tagpila kini?
TGL: Magkano ito?
As a Tagalog from the regions, I can only recognize words in a Cebuano conversation at worst, and guess the context at best.
To answer your question, I'll try to give my opinion based on three factors: availability, usefulness, and difficulty.
Availability
Tagalog, being the lingua franca for most of the Philippines and the basis of the national language, has far more available resources when it comes to textbooks, dictionaries, etc. Most importantly, since Manila is the center of pop culture it is far more easier to access TV shows, movies, songs, books, etc. for practice.
Usefulness
I am assuming that you want to learn the language in a communicative context.
Though Tagalog is spoken as a lingua franca in the Philippines perhaps it is in Cebu that you will find the most resistance. Tagalog is of little use in Cebu. Imagine trying to talk to a Spaniard by using French. Something to that effect. Though Cebuanos technically can speak and understand Tagalog that doesn't mean they will lol. I have Cebuano friends and we talk in English most of the time, sometimes Taglish and only in when we're in Manila.
On the other hand, English is widely spoken in Metro Manila (to the annoyance of Tagalog learners living here) and not all people who live in Manila speak Tagalog as an L1. Tagalog is spoken at varying degrees depending on socio-cultural factors. Tagalog could be useful but not necessary.
Difficulty
Since both languages come from the same language family, I'd say they have the same level of difficulty. Both languages also have tons of Spanish loanwoards.
Hope this helps!