Bloom and Glare not matching between different PCs

[pokoy]

I'm seeing big differences in how Bloom and Glare looks when I render previews on my workstation and how it looks when rendered on a render node - why is this? Is their size based on screen pixels, final resolution or what exactly? Does it happen because I render a cropped region for my previews and size is calculated differently when rendering the whole resolution?

Whatever it is, it really needs to be consistent so we can be sure it'll render as desired.
Btw, this is with 1.5 RC4.