It's pretty tough to compete with Vanguard products! Primarily due to the fees. VRE is around half the overall fees of XRE and IDR.
VDR is more heavily weighted, with its top 10 holdings make up over 80% of total holdings compared to 71% of XRE.
To be honest, I'm more of a fan of VDR, primarily due to the fact that it has a heavy industrial/residential exposure with big allocations to Canadian Apartment REIT, First Service and Granite.
Whereas XRE has a little more exposure to office and commercial companies like Riocan and Allied Properties.
Keep in mind though, the difference is almost negligible. Your talking a few percentage points.
Both of these ETFs are best in class in terms of Canadian REITs.
In terms of IDR, it definitely has some U.S. REITs and some U.S. specialty REITs. This would require a lot more analysis, as I just don't know the U.S. real estate market off the top of my head, where these REITs are located, portfolios etc.