Here we go.
I have two similar Philips, each of which cost me £20 (plus delivery). One from Gumtree UK and one imported from Germany’s equivalent, eBay Kleinanzeigen.
If you’re using standard VGA there’s not much between them. They differ in the details.
I’m currently using the 4122, as I have two devices connected - one by VGA and one by HDMI. But waiting on a VGA switch box, adapters, extra cables and then I will use the 4121.
20PF4121
https://www.philips.co.uk/c-p/20PF4121_05/4000-series-20-inch-lcd
From UK
Pros
- IPS 640x480
- 240p support
- better sound separation and quality
- DVI-I (accepts VGA and Component over VGA, but see below)
- RGB SCART, S-Video, Composite
- remembers last input after standby
Cons
- excessive overscan on any signal input other than pure VGA (so Component over VGA via DVI is affected)
- sluggish OSD/menu
- no indication of input signal type (in non-VGA modes)
20PFL4122
https://www.philips.co.uk/c-p/20PFL4122_10/flat-tv-with-crystal-clear-iii
From Germany
Pros
- VGA (but not Component over VGA)
- HDMI, Component (but see below)
- RGB SCART, S-Video, Composite
- very good OSD/menu
- displays input signal type (in non-VGA modes)
Cons
- non-IPS 640x480
- no 240p support
- worse sound separation and quality
- excessive image processing (“Crystal Clear III”) on any signal input other than pure VGA
- does not remember PC input after standby
@Voltz
20PFL4122 no scaling on any inputs, but excessive image processing means VGA is the only option for good image.
20PF4121 scaling and overscan on all inputs except VGA. Amount differs by input source, for example PS2 is less of an issue.
For details on getting 1:1 pixel in VGA mode of Wii, there’s a little trick involved, see Using HDMI to VGA adapters on modern consoles - #14 by matt
Hopefully this answers your question?