about oly 45/1.8mm ane PL 25/1.4mm

The 25mm has a wider maximum aperture, which gives you slightly better lower light capabilities but only slightly), and can give you a narrower depth of field at widest aperture than the 20mm, if you want to experiment with that.

I had the 20mm and never cared much for it, but I love the 25mm, personally.  It just has a lovely image quality to its output in addition to excellent sharpness, and I think it is worth the difference in cost  overy the 20mm, personally.  However, everyone has their own preferences, and if you like a wider lens or a pancake lens, the 20mm would be the better choice, then.

The 12mm is a fabulous lens, but it is really wide for everyday use.  I like it for landscapes a lot, and some indoor wide angle work, but it is not a good portrait lens, and for architectural work, I actually prefer the 14mm instead.  If you do want a tiny and inexpensive wide angle, I would recommend the 14mm f2.5 Panasonic as a nice option, also.

-J