The 455 is an easier to machine (less expensive) design which sacrifices a second bolt lug, among other things. To facilitate the interchangeable barrels and cartridges, the action, magazine well and ejection ports are longer.
The 452 was a classic, and solid, design derived from the old BRNO rimfires, and the 'American' model usually had very nice polished bluing. My preference is for the 452 & 453 models as well, although the 455 is still a good gun, in my opinion it's just not as good.