Seeing that the valve sizes are pretty similar, I'm surprised the stock 2JZ head outflows the 1UZ as much as it does. I'm attaching a graph showing the flows of the stock 1UZ head vs a stock and a ported 2JZ.
Comparing the stock 1UZ to the stock 2JZ shows improvements in flow from 59-64% on the intake side, but as much as 79-84% on the exhaust. This could mean that the 1mm larger 2JZ exhaust valve really helps its port flows.
Comparing the stock 1UZ flow to the ported 2JZ shows improvements from 73-103% on the intake, and 93-115% on the exhaust. (One of the things we already know about the 2JZ motor is that it's exhaust ports are cr*p and they respond really well to porting)
FWIW, Manley make +1.00 mm oversize valves for the 2JZ-GTE, and their stems can be cut down to compensate for overground or sunken seats. Frankly, however, I don't think anyone in the 2JZ community will say that the 1mm oversize valves helped them make more power (unless it made a marginal difference up in the insane levels above 1000 RWHP)
Bottom line for me on this, it would seem that a 1.0mm oversize valve (2JZ stock valve) or maybe even the 2.00mm oversize Manley exhaust valve (if there's enough space in the head), coupled with some judicious porting, could make the 1UZ head really rock.