OK. First lemme apologize for asking yet another question that had been asked for right about 3,357,292 times in the past. But consider this an updated, 2018 version of it OK?

Here is the deal: I have a scantly used 1TB server drive with 2 partitions. I want to back it up. The total data is around 520GB and I want to back them up into a 500 GB hard drive. I have a lot of text files so I am confident the compressed size should not exceed 450GB, actually, I expect it to be much, much smaller because I 7zip-ed a directory of 1.x GB, and after compression, the file was measly 85MB no I am not kidding, I've seen better.

All file systems are ntfs. AFAIK both utilities I mentioned in the title have the ability to "smartly" skip the "blank" (which may or may not be blank, there could already be data there just no one in the file table claims it, but I digress) area, but I want to know which one do you guys recommend - you are most certainly welcome to recommend alternatives to the 2 I mentioned.

Please understand that I had some rather unpleasant experience with clonezilla in the past. Mostly it was my fault. I was sleeping off certain operation and I woke up not remembering what I was doing so I ended up damaging certain data. Gparted on the other hand performed all my tasks perfectly but what do I know, I rarely use them since I'm more of a software guy.

Also please note:

I want to back up the bootsector, I'm usre both tools are capable of doing it but I want to be sure.

All operations will be done locally, so no ether net or internet involved.

I would still use Clonezilla, it has worked ok for me in easily restoring notebooks used for field technicians.

What I would not be so sure is the size of the final file. If you have another 1tb drive, just to make sure the created file will not overflow the 500GB drive, it would better. Otherwise, you can just try and see if Clonezilla will complain about no space left on device.

But with everything considered, clonezilla DOES skip the "empty" parts of the disk, right? Else it would be rather pointless?

Yes, it skips/compresses the empty space. Like images of 320/500GB hard disks with just windows installed fit 2 or 3 in a 8 or 16GB flash drive.