Help me Decide the Artboard Size In Illustrator

Hi Everyone. This is my first post here. I use Adobe Illustrator for my work. I am in the process of designing an infograph which needs to be printed and also be put on the web. I understand that I would be needing a 300ppi and 72ppi resolution respectively. On print the size should be A4.
Would it be wise if i create a 595px842px artboard and save it in 72ppi and 300ppi. Or, should i create a 2480px3508px artboard and save it in 72ppi and 300ppi.
Please help me understand! Thanks!!

For print you do NOT save it as a raster image.
If designing in Illustrator, make sure your RES (raster effects setting) is set to 300ppi and work in full scale. Your output file will usually be in the form of PDF or packaged native file depending on the preference of the printer. Ask Them!
DO NOT FORGET YOUR BLEEDS on the printed piece.

How you dump it out for web depends on how it is intended to be use. Remember low rez type can be hard to read.

Your understanding is incorrect.

For print, as PrintDriver mentioned, you do not rasterize the vector work done in illustrator to a fixed resolution. Instead, you let it remain as vector art to be rasterized at the maximum resolution of the output device, which is often thousands of dots per inch.

The 72ppi rule for digital displays is also wrong, misguided and should be immediately forgotten as though you never heard it. Old Macintosh monitors from 20 years ago used that resolution, but modern displays are much higher resolution. Even then, though, it was a meaningless concept when preparing graphics for digital use.

When it comes to digital displays, you shouldn’t be thinking in terms of how many pixels are in an inch since it’s, well, meaningless. Fixed linear measurements, like inches, pertain to physical objects in the real world that don’t change size (like a sheet of paper), whereas a digital image displayed on a monitor might be an inch wide on one monitor and only three quarters of an inch wide on the next.

Instead you should be thinking in terms of how many pixels you need to fill the space. In HTML, for example, images are defined by their pixel dimensions, not the number of pixels per inch. If your website page is, for example, 1000 pixels wide, and you want to fill exactly half that width with an image, well, that image should be 500 pixels wide (how many of those pixels might be in an inch or a centimeter is a meaningless concept).

Also, back to vector imagery. Today, Illustrator imagery that will be used on the web can also remain in a vector format called SVG. Depending on the situation, you don’t need to rasterize it.

Finally, your question about what size to make your art board… For print, you make your Illustrator art board large enough to accommodate what your’e working on. If it’s an A4-sized flyer you’re working on, the answer should be obvious.

If it’s something you’re working on for digital display, make it whatever size you want since it’s mostly irrelevant given that vector art can be reduced or enlarge as needed. Just make your art board large enough to accommodate the detail you’ll need. For that matter, I don’t even bother with setting up the dimensions of an art board when I’m working on things for digital display. I just draw it at whatever size might be needed, then adjust the art board and the images to fit when I’m finished, whether it’s SVG, PNG or JPEG.

Of course, if you know that the Illustrator image is for a website and that image needs to be 500 pixels wide, a logical measurement to use in Illustrator is points since an informal relationship has sort of developed that equates pixels and points — even though they’re totally different things.

Thanks @PrintDriver. The understanding gets better now.
How much bleed (max. and min.) do I leave for the printed piece?

Thanks @Just-B. It’s best that I get to designing on A4 for the print. Maybe, understand his web space requirements and then proceed to align it for the web. Thanks!