Here are some thoughts for you:
Interestingly, RISD has the edge in the Design Intelligence rankings. I don’t have the 2016 edition but a quick internet search places RISD at #6 while CU is not in the top 10. Historically, RISD has bounced between #5 and #10, while Cooper has been all over the place in the top 15-20 range. Looks to me like it’s ranked more similarly with Pratt, at least per Design Intelligence.
RISD is the #1 design school in the US and for architecture specifically is the highest-ranked dedicated design school and typically the only one consistently in the top 10 (competing against some pretty high quality university programs!). That is a significant selling point regardless of other features (such as the close affiliation with Brown, a dedicated campus, etc.). RISD also gives you flexibility in case you opt for something else. While being one of only 30 selected students is certainly prestigious, you need to ask yourself whether that’s a critical mass of fellow students for your first year of studies. One of the main selling points of RISD is that your foundation year will be similar to that of the rest of the first year class (approximately 400 total). You will probably take Foundation with your cohort and get to know those kids very well. But your course of study will be similar to everyone else which allows you to bounce ideas off of future artists and designers of all stripes.
There used to be concerns about CU’s financial stability but hopefully that’s resolved with the new tuition program. RISD has had its share of academic tumult with the previous president but the viability of the institution never appeared to be at stake.
On the other hand, CU is a highly selective program (more so than RISD), would allow you to begin your program of study immediately, and includes the standard math and physics courses (which for the life of me I can’t find anywhere among RISD’s arch. course selections - not even as electives). RISD also offers the BFA in Architecture so if the B.Arch is your goal you’ll want to check to see how many of those architecture majors actually stay the 5th year and pick up the B.Arch. Finally it appears from looking at the numbers that RISD accepts about 30 architecture majors per year so about par with CU.
I took a look at test scores because RISD is known for attracting bright kids but CU definitely has the edge on this one, especially in Math (which I’d expect to be an important factor for architecture!). From College Navigator:
CU (Mid 50% range)
SAT Critical Reading 600 730
SAT Math 650 770
SAT Writing 610 710
ACT Composite 30 34
RISD (Mid 50% range):
SAT Critical Reading 540 670
SAT Math 570 710
SAT Writing 570 690
ACT Composite 27 32
ACT English 27 34
ACT Math 27 33
Of course, CU’s engineering program influences these high test scores but having that engineering influence would actually be an advantage for the architecture program, IMHO. While a RISD student may be able to take engineering courses at Brown, that strong technical influence wouldn’t necessarily be part of RISD’s culture and one can certainly graduate from RISD in architecture w/o taking any technical courses (outside of what’s required for the B.Arch specifically) or w/o even being around other students who think BOTH technically and conceptually.
Some other thoughts: CU has about a 70/30 male/female ratio, and it’s the opposite for RISD. In terms of urban surroundings, the closest major city to RISD is Boston about 50 miles away. While remaining in NY can be pretty cool for an architecture student, there is no doubt that RISD kids get internships and jobs in NYC as well.
Good luck with your decision!