This is a question, but it's really based on personal opinion so I'm not marking it as a question thread, because I don't feel like I could clearly say that one answer is correct.

I grabbed 6-8 and I wanted to give them a try, but it turns out 6 and 7 are significantly older than I expected them to be. I kind of want to ease myself into the game by starting with 8... but if it has additional features that make it seem better than the older games I feel like I'll be biased and not enjoy the older ones as much even if they might actually be better in some respects...

TL;DR: With the intention to eventually play all 3 (maybe even all 8?) where should I start?

Start with 6 and import your characters into 7.
Wiz 6 had an old fashioned UI and no auto-map, though...

You'd definitely want to play in order for plot reasons since some aspects of the sequels are affected by choices made in the preceding game; nothing too major but it's a nice touch, and of course you have the added investment factor of continuing with the same characters.

Either version of Wizardry 7 will work for progressing through all three games with the same party. GOG installs Wizardry Gold by default; you can get the DOS version from the bonus content downloads.

I recommend starting with 8, you don't miss out on much plot because they give you the jist of it anyway… 8 is far and above the best engine so you will have a better experience.

p.s. mild spoiler… there is more than one ending and certainly more than one type of party | play-style so it's not like you can't have another go.

Okay, atm my intention is to start from 6 and work my way forwards.

Thanks for the recommendations, all.