All I can say is that maybe there's something's strange with my computer. Dell support says usually my problem is caused by the CPU or maybe the RAM. But I think it might also be the motherboard. It's not the top-ranked  motherboard, It's a B550. 
 
That's why I'm returning it. For the money I paid (UDS 5600), I had the right to expect a computer that delivered more


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA

Hmm wish I could get your PC, but we don't have that option in my country. ☺️

As Animagic states, your New PC seems to be very capable and slower result on SSD seems to be contrasting result from other members that tested a simple scene with me last month in my benchmarking thread.
We all had fastest render on SSD with both MP4 and AVI.

Still your scene must be pretty heavy.
All the best from me.

That is a peculiar result and in contrast with my own experiences with the same type of PC.  Also, the CPU shouldn't really have that much effect on rendering times. I'm thinking there may be something wrong with the build.

I usually build my own PCs as well, but last year it was impossible to get an RTX 3090, so I went with Dell.

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I'm finishing a movie just now, to be posted soon. It's rendered in MP4 but in 4K. So I'm serious about the quality. For my next movie, I intend to render in AVI uncompressed. I just learned of its benefits too late.

As far as rendering to my SSD, I tried that with my new computer. It takes longer than if I render to my HDD. Almost wice as long.

That's why this new Alienware Aurora r14 from Dell is going back! I'm going to build my new computer myself, like I used top. Dell gives you some choice of components, but not enough. As for the CPU. for example, they don't really give you the choice. I wanted a high-end Ryzen threadripper like in my old computer. I got a lowly Ryzen 9 5950X. Dell gives you what they think is good for you and what they can get away with. I'm very disappointed with my new computer. Like I said, it takes FOUR times as long to render as my old  computer Now if it took TWICE as long that would already be prohibitive, but FOUR times!? Are you kidding? This computer is going back.


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA

Before that try an AVI test instead of MP4.
As you may have issues in warranty of.your Prebuilt  PC the new one which you have purchased.
All the best... And do get a good SSD for video outputs.

Thank you for your help, sungod. I think I may transfer my Ryzen threadripper to my new PC.

My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA

That could be the case.
You may want to try render on an SSD and not a HDD and try AVI uncompressed. But both SSD should be same.

But I think you can leave above test and carry on with MP4 and forget about the difference.
CPU does makes difference in MP4.
I went from 6 core Intel to 5950x and I had huge boost.with same GPU.
So Same GPU with more Powerful CPU did give me gains. I will suggest a good nvme M2 ssd as your next investment to unleash your rendering speed. But as I have been reminded by more experienced members it's about quality renders and I don't compromise on quality but do try to keep rendering as fast as possible.

Yes, in my old computer (which I built myself), I have a AMD Ryzen threadripper 2970VX 24 core 3.0 GHz.
In my new Alienware from Dell, I have a Ryzen 9 5950X 16 core 3.40 GHz
So, the fact that my older computer seem to have a more powerful CPU (more cores) and more memory,  could that explain some of the loss of rendering speed.?


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA

Additionally try a small project too from scratch.
Single character 
Some talking Animation.

Also can you tell which CPU are in each of those PC.

Yes. I'm waiting for another call from the Dell technician  at 2:00 PM today  and then I'll try to do the benchmatrk. Thanks.


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA