As someone who just watched a Laserdisc over CRT a few minutes ago, I guess I can speak to this one with a bit of experience:
Resolution depends on the viewer. Some people make a bigger deal over it than others. As a note, DVD via component is sharper and less susceptible to noise than LD over composite.
LD Players vary on their output via the type of player. Higher and more expensive model LD Players often have higher quality parts and put out less noisy pictures. I'm running an NTSC Pioneer D704 LD Player and the colors look great. They are sometimes closer to the actual film prints of the time than digital remasters, but don't tell anyone that in the BluRay section
Since you are in Australia though and are using PAL, the Laserdisc story is a bit different. PAL LDs are often just transfers of NTSC masters. The picture benefit is minimal. Unless your collection or player mostly NTSC, you are unlikely to really benefit anything from the PAL releases.
As far as a line doubler goes, 1080i should be fine for regular "legacy" inputs. If you have the option, try 960 to reduce unnecessary banding (i.e. doubling the image exactly)