Go with the last one, the 5 1/4" speedbase. The other two aren't baseboards you'd put by themselves in a house, they need a basecap with them and I don't get what the groove is supposed to be in the second one. Put on one coat of paint, install, putty nail holes and then second coat of paint. You'll need a miter saw to do this job.

Then put down oak quarter round or shoe mold stained to the same color as the floor and clear-coated. With wood floors, the quarter round should be stained, not painted.

If you need to caulk gaps at the corners, do that with painter's caulk before you put the second coat on.

The 3rd is nicely transitional. I'd avoid the other 2 because of their very square corners. MDF is easily dinged and square edges show dings prominently. And secondly, dust settles on horizontal surfaces better than it settles on vertical ones. The 3rd profile has a very narrow top surface but the other two have about a thumb-width of surface that will happily gather dust.

I wouldn't use MDF. I'd use wood.

I wouldn't use HD for any interior moldings. See what your local lumber yard stocks, hopefully they will be longer than 84" (you should be able to get 16' ers)...

Are your current baseboards continued throughout the house? I think that it looks better if all the baseboards in the house match. Do you dislike your current style? You could take a piece to a lumber yard and see if they have a match in stock.

If you don't have a miter saw, you can use a miter box and a hand saw (and a coping saw for the inside corners).

I like the first one, Paint first, put in with finish nails then putty and paint over nail holes / finish caulking after installed.

Use the third one. The first two don't look like baseboards to me. Measure and cut, then prime and paint, and then install. Use wood putty to fill the holes. Then caulk.

I prefer the first one. I see similar in more contemporary and modern homes, and is very similar to the baseboard we are putting in our new home (definitely not with quarter round or shoe molding - I would avoid that if at all possible). I don’t know any baseboard that won’t collect dust, but at least with those it is just in one spot, not along multiple grooves!

MDF in my view is preferable if you are painting it anyway.

I was thinking MDF since I am going to paint them white anyway, and it won't split when nailed and it's straight. Most probably I will need to install quarter round because we will have floating floors and I need to hide the expansion gap. And Although I like the first one probably it won't look good with quarter round...

If you're cutting this and putting it together, primed fingerjoint or clear pine is a better option. MDF doesn't make very sharp cuts, doesn't sand as well and just doesn't stand up like wood. Get as many 16 footers as you have long walls. Start by cutting the one for the longest wall first and then go down. Unless you have a lot of short spans, 7 or 8 foot pieces will require joints, which will show. Watch several Youtube videos on cutting and installing baseboard before you start. It takes more skill than you think. And did I say don't use MDF? Don't use MDF.

If the 3rd feels too ornate for you, here's a very spare modern profile that angles at the top. https://metrie.com/products/CVS2C2PMD/

Consider a simple profile with both straight and curved lines:

Overall, the above profile is more rectilinear and modern but the slight curve helps soften the the geometry and allows for a more transitional, timeless look. In addition, the minimal detail allows for low maintenance care when it comes to dusting.

Best of luck with your project!

Nanke's profile and the profile of the speedbase both originate from the same style, a 1x8 pr 1x9 pine board and basecap on top. Both will work in all areas of your home.