For real-time viewing, you’re probably better off with the external hardware processors you are currently using. (You don’t say which LD player you have - this is the most important part of the chain!)

However, there are some improvements that you can do with a capture and post-processing that are not possible in real-time, eg:

multiple capture average/median, to remove dot crawl, random noise and dropouts without damaging detail
use a high quality motion compensated deinterlacer (too slow in software for real-time viewing)
even better, for film-based content with 3:2 pulldown you can carry out IVTC to get a true 24p output (although some hardware processors can detect a pulldown pattern and do this in realtime, maybe the VP50 does?)