Which Mac device is best for financial trading?

Any Mac will work for that. That is not particularly demanding work.

Check your budget and pick one that fits it.

If you want a desktop, go for a Mac Mini and get a monitor that works for you.

If you want a portable one, get a MacBook Air.

No less than 16GB of RAM. Storage is up to you and your budget.

Remember, neither RAM nor Storage can be changed after purchase.

if the question is "how many displays", that is more complex than what you asked.

The Apple standard for its built-in hardware-accelerated displays, makes them suitable for full-motion video for production/display of cinema-quality video with NO dropped frames, and NO dropouts or partial-blank scan lines due to memory under-runs or other issues. This requires a hardware rasterizer/display-generator for each fully-accelerated display, supported by Huge memory bandwidth to refresh each display 60 or more times a second. 

With one minor exception, the same rules we learned for the M1 and M2 still apply to the M3 models. Display interfaces are generated deep inside the system on a chip. How many there are depends on the exact type of Processor:

M3 (plain) like the 13-in and 15-in supports up to ONE External fully hardware-accelerated external display.

Except the M3 MacBook Air models with 13 or 15-in display, (and certain M3 plain MacBook Pro models when running 14.6 or later) which can support a second external display instead of the built-in display when you close the cover on the built-in display.

M3 PRO processor supports up to Two fully hardware-accelerated external displays.

M3 MAX processor supports up to Four fully hardware-accelerated external displays.

M3 ULTRA processor supports up to Eight fully hardware-accelerated  external displays

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next, you have to decide what KINDs of displays -- do you need all displays to be full motion Video?

If and only if you are doing ONLY program listings, spreadsheets, stock quotes and other slow to change data, there are some other solutions, but they require you to make some strong compromises. You can add some additional "fake displays" that reproduce the picture, but FAR slower than real-time. Each additional "fake" display requires an external "stunt-box" that holds some display hardware to generate the data stream to send to an actual display. Using a mouse on such a display can make you feel queasy.

You should be considering what platforms are supported by the financial trading software that you want to use. Are there operating system restrictions such as Windows only, or restricted by an older version of macOS that is unsupported on current new Macs? Better to do the upfront assessment than to post back here that the selected software does not work on your new Mac.

Per the above, what are the hardware configuration requirements for that trading software?

The answer to these questions will help you decide on hardware selection.

I do not perform trading and cannot recommend any trading software.

Your challenge is whether any trading software can be natively installed as a Mac application on your Intel MacBook Air that is still running Catalina or if it is Windows-only, whether you meet the RAM, storage, and processor/GPU requirements to run that software in Apple's Boot Camp. The MacBook Air would not be a good choice to run heavy software in a Virtual Machine as a Windows guest. The Air would simply overheat.

alirezamousavi110 wrote:

and what about mac studio ?is it better than mac mini?

Yes. but its also. much more expensive and overkill for most tasks specially what you describe.

and do you sure that MacBook air is enough for trading and new MacBook pro is not nessesery?

Yes. As I said, trading is not demanding work. The MacBook Air is plenty powerful.

and if i buy mac mini or mac studio can i connect several monitor(4 or 6 monitor) to them without any problem( like hanging or reduce the speed or freezing os and....)?

Yes. The Mac Studio can support up to 8 displays. It won't be slowed down. If you need that many displays, then the Studio is the only option.

and how about iMac ?which one of iMac and mac studio is better for trading?

The iMac can only handle one additional external display.

Either one will work fine for trading. It is not demanding work.

If you really want the Mac Studio, get the Mac Studio. Its very, very expensive but is very, very, very powerful.