I have a new pc using my old dell 17'' 1280x1024 monitor. The text and some things like the taskbar and windows logo on the bottom left are smaller.
I've made sure all the settings from my old system are the same, resolution, changed dpi, adjusted clear type text, made sure all the drivers for the motherboard (asus b150) are updated. I've actually changed the dpi and clear type text numerous times since Tuesday when I got it.
The driver updates helped the most, text is better but some other applications I use still seem smaller (utorrent for one), and the icons on the taskbar seem smaller than they did with my old setup.
My old pc was using a sapphire 5450 512gb graphics card to handle the display, my new pc is using an intel i-5 6500 with an integrated intel grpahics 530 which I'm told is supposed to be better than my old gpu. I don't know if there's something in that which could be causing this, I'm pretty sure I'm not imagining it.