I have to put a disclaimer right at the start of this post. I have a vested interest in either answer to this question — I set up instruments for my customers and I have written a number of guides on guitar and bass setup. All of that said, I’ll just try to lay out the considerations for you and you can make up your mind as to the best path for you.
Make sure it is ‘Professional’
The key word is ‘professional’. If your tech/repairer/luthier is good, they will probably be able to to get things that little bit further than you can on your own. Their experience will give them an advantage and they'll be able to discuss your style and can advise on a setup that's right for you.
Of course the other side of the professional coin is that you need to be able to trust your setter-upper. There are, unfortunately, some people that either don’t know or don’t care and, if your guitar actually benefits from their work, it’s probably luck. I’m glad to say that these people aren’t the majority but they do exist so get some recommendations from friends and musos.
If you’re doing your own setups, you don’t need a lot of tools but there may be an up-front cost for some. Many tools you might already have but stuff like nut files are definitely not cheap and they make a big difference if you’re DIYing.
Of course, if you think you might set up more than one guitar or bass, or you feel you’ll regularly tweak your instruments, that up-front investment can really pay off.
Paying a pro to do a setup for you instead isn’t super-expensive but that cost can add up if you’ve got a few guitars.
Maybe you don’t want to spend the time getting to understand how to set up your guitar. Maybe you don’t have the time to actually do the work. Paying someone else will certainly save you some personal investment of time.
On the other hand, lots of techs will have a turnaround period where they’ll have your guitar and you won’t. You might need another instrument to play or gig with while the work is being done. Some — terribly enlightened — repairers (ahem) will be able to pre-schedule appointments to minimise the time you’re without your guitar but you should factor in some guitar-absence time if you decide to ‘out-source’ your setups.
Ah, yes. It can be a bit scary. And, even if you’re someone who’ll happily start attacking guitars with screwdrivers, there’s always the chance of making things much worse than they are currently.
Well, the good news is that there’s heaps of information on the internet. The obvious ‘con’ on this is that it’s often hard to determine what’s correct and what’s just some forum-posters strongly-held opinion.
Slightly safer might be a good book. I can really recommend Dan Erlewine’s How To Make Your Electric Guitar Play Great. It’s crammed full of incredibly useful information and Dan is most certainly The Man when it comes to all things guitar.
If you’ll allow me to toot my own horn, my Sketchy Setups series are super-simple and friendly introductions to setups. And, I’ve dedicated a guide to each of a number of different instruments so you don’t need to read about Strat tremolo bridges when you’re setting up a Les Paul.
The Bottom Line
Leaving the tool requirements aside, choosing to do your own setup — and doing it well — means an investment in time and thought. As with pretty much everything in life, that investment can really pay off if you work at it.
The ability to set up an instrument well will mean your guitars will play exactly the way you want them to. It will mean you can make whatever seasonal adjustments are necessary to keep them that way. It will mean you can do things on your own schedule and don’t have to translate the wants in your head into actual words that a tech can turn into guitar adjustments.
But, it’s not for everyone. And that’s cool. Many players don’t care about the nuts and bolts and just want someone to help them get a guitar to ‘fit’. If that's you, find a tech/repairer/luthier that you can trust and have them take care of your guitar.
When the toilet’s blocked some people reach for a plunger and some phone a plumber. There’s no wrong answer here. Do what’s right for you.