What are your goals?
Staying with a non FMS single pilot turbo-prop is certainly more interesting flying...
Might make you more $$ in the short to medium term, and you might even like the job better.
Career wise, if you want to fly the heavies, move up and get a seniority number ASAP.
But if it quality of life you want, the choice is not so simple.
Yes...I have flown cargo in Metro 3/ Merlin's IV, along with others....
If you like getting to park within sight of you plane...having days free, and getting to hand fly, then cargo is better.
Move up...you become a systems manager...
Less actual Flying, more planning and managing a crew and the situation.
Less ability to make choices that affect things...
I like to say flying 121 sometimes is more fly flying with a flow chart...
Not a lot of judgement, or when you compare it to 135.
That's what makes it so safe, but also can make it overly routine.
Sure...some like saying I fly for...
Then walking through the terminal in a uniform...

Simply put...do you like to fly cause you like to fly, or because of what it can get you?