Magix supports both the 44xx series sets and the older MLX sets, of course you need different station cards to support 44xx, MLX, and Partner phones.
Among some differences:
Partner sets with displays have adjustable backighting.
The current series of partner sets have 2 line by 24 character displays; only the 12 and 24 button 44xx sets have full 24 character width.
Partner phones have a base stand with three adjustable angles, and can be flipped over for wall mounting. In addition, the displays themselves have three adjustable angles. (I personally find the lighted, angled display one of the best features of the partner phone.
Only the 44xx sets have built in separate headset jacks with independent control. Both Partner and MLX sets require an exernal amp/switch box that plugs into the handset jack, though MLX sets provide buttons to control the handset jack (so you don't have to lift the handset to use the headset.)
MLX and 44xx sets use digital signalling, potentialy a plus in areas where RF interference might disrupt a traditional T/R line.
44xx sets have a T/R adjunct jack for attaching gadgets. (I don't know if they get a separate station ID.) MLX sets (some) can be equipped with a MFM module to give you a T/R jack with its own extension. Partner sets have a T/R extension jack that shares the same station ID as the Partner phone. All the partner phone buttons are useful while using the attached T/R device.
You can get some quick at-a-glance views at
Legend/Magix support of Partner phones doesn't mean you get all the Partner features, but sure seems to preserve some investment when upgrading. I do not know if the Partner adjunct Direct Station Selectors (24 and 48 button models) work on Legend/Magix.
Labeling Partner phones is a damned nuisance, since to do a good job of it, you need prepunched forms and (free) software to print nicely on the forms. Line/Feature buttons are tightly spaced (so a Partner phone with equivalent number of buttons to either MLX or 44xx phone is smaller. Desk space savings may be a feature, but there's less room to label each button, and the blank pre-punched labels are expensive. MLX and 44xx phones have large label areas using rectangular cut-out paper. You can buy these, or, you can just print nice labels from your computer on standard paper and make 4 straight cuts. Having someone at the office who can run off new labels in minutes at essentially zero cost makes it easy to keep everything professional looking.
It would be enjoyable to hear some other comments, particularly about the aesthetics of the various phones. I still think the orignal Merlin (ATL) classic phone were the best looking, and am not fond of the round buttons on Partner and 44xx phones.