It depends. If all you care about is as much horsepower per dollar, the base Z is the better buy. If you care about things like interior quality, more equipment, etc but only have low to mid 40's to spend, the 2.0 might make more sense.
If you're cross shopping any 3.0 Supra with a Z, the Supra...
I doubt it. Monaco is too slow. Those characteristics are not repeated anywhere else on the calendar. To build a car for that track would be silly. The track is so tight, they need a special steering rack just to get around the hairpin. A regular rack doesn't turn tight enough lol. By "slow"...
$5k difference between a Performance spec Z, or a 3.0 Premium Supra that's lighter, faster, better built, with better quality parts, and much better looks. Easy choice. And that's before any markups.