Sier spends a lot more time in the guts. lipinski is about the 8th midfielder in line so gets put onto a forward flank a lot. I think Sier is judged harshly by the club for more than his output. His games at VFL have more than deserved a recall when we've had much more senior players spudding it up.
Lipinski has scored 2 goals this season (1 more than Sier) and averages 1 more score involvement than Sier this year in a much higher scoring team.
Again I'm don't know enough about Lipinski to judge. But you're basically buying him on potential rather than proven experience/output. And it's a position (midfield/wing) where we're not exactly lacking in terms of potential (Daicos x2, Macrae, Bianco, Reef, Poulter who will need opportunities going forward).
He's been in the system just as long as Sier for 5 years now in a side that has made a similar number of finals appearances in that time and failed to establish himself as a best 22. If we have ambitions to be a contender again I don't see how getting players that are not good enough for other contenders will help us get there. And if we're buying on potential, I'd rather players who have had less years in the system like a Dylan Stephens who might have higher upside. Prefer to walk him into the PSD over Lipinski.