Oddly enough I have one of those! I know two former 928 owners and even more former Porsche owners. Based on info from that group I would recommend 928 ownership to the level of... a poster, framed or not, I would leave that up to you!
928 was placed in motion pictures (Looker) and IIRC was to be the new flagship for Porsche. I don't think either of two would:
Recall many if any fond memories about that car.
Recommend that anybody should seek to buy a 928
I was offered the one car as payment for some work I had done($4000 total)
Not all 928s are these two examples but image wise unless you see the front you are looking at 924/928/944?
So my opinion on 928 is old tech/style that way further devalued by cheaper lookalikes. You are talking about lower mileage but the time factor will make this car far more need, IMO. But as a pro Porsche parts are available everywhere and very affordable! Which is good you will need lots
The Lotus would/is probably on one or more of the "if you can, you must own this car" list. I guess it sort of looks like some other cars... All styling seems to come from the same CAD file these days. It doesn't look at all just like a cheaper weekend thrasher car. I don't think any comparison would have a classic come out ahead of new technology... handling, reliability, ergonomics etc.
If those were your only two choices my opinion is you don't really have a choice.
Now if you are a Porsche guy you still don't have choice because while while conducing your prepurchase inspection you turned up that the head bolts, which were properly torqued(using torque wrench #PMC56378931-6789a, which was calibrated on 2/13/2004@ 17:03.27 at the Stuttgart Cal lab by a guy named Otto, verification was performed by inspector# 32590.)
My opinion? If you think the last bit about head bolts and torque stuff, if true, is good news. Buy the 928, you are a Porsche guy! Otherwise I would recommend the Lotus.
But I would also recommend a look at the new Alfa Romeo Gulia. IMO that would be a much tougher choice.
Regards