Format for 60x75 inch Gallery Prints - 4x5 or 8x10?

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This might seem like a dumb question, but please bear with me.

I use MF digital usually, but want to get into LF for my fine art work as I am tired of stitching.

Next week, I plan to buy a 4x5 or 8x10 Arca Swiss F-Metric Compact (or similar).

I shoot primarily 5-second (plus) exposures of landscapes and interiors (devoid of people) in color. My prints need to be ~60x75 inches (strict requirement). In terms of workflow, I drum scan, modify in PS and print digitally.

My questions:
1) What is the absolute best ~150mm (or comparative 8x10 normal lens) lens I can buy for each camera?
2) If I use a top Rodenstock or Scheider normal lens, will I be able to achieve a high quality 60x75 inch print, with solid tonality and detail, from the 4x5 (which I am leaning towards this due to size considerations)?
3) Assuming I use excellent technical skills in either format, what will I gain by shooting 8x10? In other words, will a 60x75 inch print (landscape) from an 8x10 look THAT much better or different and how so?

I understand well how 8x10 film stores more data, but I'm particularly curious whether prints at the above size will look that much different if I use the best lens I can.

Thank you in advance for your input.

PS. I want to stay away from 5x7 due to my aspect ratio preferences.