Portland's auditor recently issued a finding, that in Portland, areas with Urban Renewal funding have higher property values than areas without Urban Renewal funding. Even if that is your goal (Should it be? Why is expensive property a public good?), what kind of comparison is that? "Massive, wasteful spending" vs. "no spending at all"?
The problem is a lack of "political clout" among alternative revitalization approaches, to make a case for a comparison. For example, CDC's can efficiently create jobs with community-driven revitalization and incubation programs, but these are not compared with Urban Renewal. They should be. If you compared the economic benefit of government small business aid programs (all of which are gone now, like CITA from the 1970's) the efficiency of public benefit, as contrasted with Urban Renewal, would be extraordinary.
Having impoverished community-driven development in the past 20 years, Urban Renewal has eliminated the competition for tax money, freeing it for gentrification projects. Luckily, we can still refer all Urban Renewal spending to the ballot, but there must be organized opposition to do this. Most people aren't close enough to the City's schedule to know when it is possible ... but whenever you hear about "expansion of an Urban Renewal district" or "raising the spending ceiling on Urban Renewal", you can bet that someone is pushing to destroy some affordable neighborhood to benefit landlords and private development interests. If we all pay attention, and refer spending to the ballot, we can stop this horrific practice, in our respective Cities.