OK, so Steve (Digital Dream Division) kindly offered to send one of my own tunes up for the Landr treatment, since he's ponied up the monthly fee for the full service. Thanks, Steve!
I'll post three versions of it on my SoundCloud page: the unmastered version, my home-mastered version and the Landr-mastered version, so that you can hear and judge them for yourself. Links at the bottom of this post (I'm uploading them as I write this).
I have to admit, the results are better than expected. Their version is more aggressive and brighter (even though Steve asked for the Medium treatment) than my own. Average RMS was a reasonable -12 dB, only slightly higher than mine at -12.8 dB. Can't accuse them of squashing it to death in the name of "radio-ready".
The biggest difference was EQ. Here's a screenshot. The green line is the Landr master, the white line is mine. The analyzer is set for a 4 dB per octave slope; the difference looks greater at my usual 4.5 dB/oct setting. That's about a 6dB bump at 3.5 KHz.
There were definitely some elements that sounded better than in my own version, in particular the drums and percussion, which were better-defined due to the added brightness.
I did not, however, feel that the vocals and guitars benefited at all from the added 3-4 KHz bite. The lead guitars in particular sounded buzzy and thin and made me grit my teeth. However, this could be my own prejudice from having heard them differently for so long.
EQ wasn't the only change. As a comparison of amplitude histograms shows, the Landr master had reduced dynamic range over my version, with fewer quiet parts. You can hear this as greater apparent loudness.
I admit to a personal preference toward classic equalization curves, a prejudice probably formed in my early years when I listened only to classical music, up until about the age of 13. That's when I was corrupted by rock 'n roll and my hearing acuity began its decline. But even the prog rock stuff I cut my teeth on in the 70's typically had a 5 or 5.5 dB per octave slope, which sounds very different from today's brighter chart material at 3 to 4 db/oct.
In other words, maybe I just like a mellower EQ because I'm an old fart.
Here are the links (both are 256 kb/s MP3s):
My version The Landr version Want to try your hand at mastering the same tune? Here's the
unmastered version (66MB FLAC).