The 67 series is basically a larger version of the Printmaker 35. It's a single column enlarger that'll handle up to 6x7cm negs. The 23C series is a twin girder enlarger, and is considered a step up from the 67 series. There are a wider variety of accessories, and it'll handle up to 6x9cm negs.
Which is better in real life probably depends on condition, and what accessories come with them.
The 23-series will also print up to a 6x9 negative while the 67 will do
up to 6x7.
You can also tilt the head on a 23 and project onto a wall for huge prints
if you have the need or desire to do that. I don't think the 67 will do that
but I could be mistaken.
Negative holders and lens boards are also much easier to find for the
23-series enlargers and in more variety.
But, the 67 is lighter and more compact if that is important to you.