Roll for meriln or use friends?

The benefit of having your own Merlin is customisable CE builds and the potential to run double Merlin.

It's not necessary per se, as it's almost guaranteed that you'll always have at least 1 friend with Merlin. But if you like to be independent, then do so.

He's one of the best servants support wise and probably only Waver can rival him in that department for a very long time.

But the most important question is: Do you like him?

FGO is not a difficult game and you can get quite far relying on free 3*s and good friend supports if you know what you're doing. So the strongest defining factor is whether you like the character or not.

for me the point is thet he is so good you can use him alweys, but not all other servant can. so if you roll him, you can use any friend damage deal any time, but if you roll someone else (lets say gilgamesh for exemple) you cant use him all the time.
becouse you (like me) are relativly new to this game, i suppose you dont have a good aoe and a good st for any challange.
Still, Support Strenght is their skill, while most of the damage dealer have good damage even whit low level skill.
support need to be 10/10/10, and meaby whit 2030 ce, pretty rare .
Mmmh. hard.
Still, i like to be the damage dealer, so i usually prefere to summon support from friend and use my own damage dealer.

Using friend's Merlin is Op enough. But dual Merlin is broken.
Because
(1) dual 2nd skill almost guaranteed to save your team in every circumstances. Except enemy have anti-Invincibility skills/NP. That is quite unique than Waver/Hans.
(2) dual NP accumulate snowball effect in Critical team

Honestly speaking, I hate Merlin's broken to the game which made DW put more and more tough quest in the future, typically multi-hp bar boss. However, when you meet Merlin's banner, then ROLL.

1)Since you're kinda new,I think it's worth trying your luck in Merlin's banner for better units.
2)one of the benefits of having him would be in case of quests in which you can't pick a friend and have to rely on your own units