My opinion is that the best budget over and under costing less than $1,000 is a semi-auto. Unless you got a heck of a deal on a used Browning Citori or Beretta 686.
Here is my reasoning:
If you're asking this question online, you're probably not well acquainted with over and unders and like the look. That's okay! Here are some of my talking points:
A 686 or Citori will run about 30,000 rounds before it needs service. Gunsmiths that can do that service are plentiful and parts are common world wide. These guns can run over 100,000 rounds. You will not wear it out.
The CZ and Tristar and other importers are sourcing guns out of Turkey because (among other things) the Turkish Lira has been catastrophically devalued and the skilled labor is now about one fourteenth as expensive as it was a decade ago.
One of the big differences between a $2,400 Beretta/Browning and $900 Turkish gun is quality control. If you're lucky, you can get a great value and very solid shotgun right out of the box. If you're not lucky, you had best go with the company with the best warranty and reputation for service- because you might be sending that gun back to the factory several times to get problems ironed out. I have heard from fellas in both camps over at ShotgunWorld. Service: CZ-Outstanding. Tristar-Really Great.
Looking inside, you'll see that the B guns are machined like swiss watches. This level of quality is also applied to the sear and hammer and trigger assembly. You will have a good smooth trigger pull. The firing pins are built with the expectation they will go 30,000 rounds.
The $900 guns are built for the average hunter who does not know that an 8 pound trigger pull is making them pull shots and we only expect it to shoot 250 rounds per year (or less. I bet the average guy only shoots a couple of boxes a year.)
Value- if you buy a used Citori or 686 for $1200, you can sell it in 3 years for $1400 or more if you take any sort of care of it because people trust it won't go bad. They don't. Your $900 shotgun you can resell for $350 because it no longer has any warranty and people know they do stop working.
Now, the most important thing about a shotgun is how it fits, because you aim by looking, not by aiming like a rifle. It must fit.
With an over and under, unless you are lucky, you must be very picky about which stock you use. The Browning is a neutral cast and is a bit heavier, the Beretta has a bit of cast and is lighter. I shoot a Syren which has even more cast, a very short length of pull, and a monte-carlo stock. Because it FITS ME.
A semi-auto is much much easier to get a proper fit, because it's "modular" in some ways. They have shim kits that .. well, you know. They adjust the cast and drop.
That idea of the modularity applies to the trigger group, as well.
If you buy a $600 semi-auto, expect to pay $85 to get a trigger job done. Someplace like
https://www.thefirearmsspecialists.com/
You're not shipping the receiver for a trigger job (over/under) just the trigger group. HUGE difference in shipping cost and hassle.
There are lots of solid semi-autos in the sub $900 category. NOT Beretta or Browning, by the way!
Decide if you want gas or recoil operation and... Tristar is well regarded, so is.. Impala. See the video by Randy Wakeman.. I trust this guy.
https://www.youtube.com/watch?v=T9Qhnl8GL4U
So.. to be harsh.. a cheap over and under is like a VW beetle with a fiberglass ferarri conversion kit on top of it. It looks cool, but it's not a sports car. And only kids are fooled!
Do I have a cheap Turkish shotgun? Yes. But I can do my own trigger job, can gunsmith the entire receiver, and have many really nice backup guns that are joys to shoot and carry. My side by side is just plain cheap fun and I got mine used for $500 from my neighbor. But he had a couple hundred rounds through it without trouble, I knew he was not selling me a problem child.