This post is OPINION based on personal experience with both brands:
Having owned both Catalina's and CS's I can assure you there is no comparison when it comes to build quality.
While Catalina's are fine boats they are not anywhere near as solidly built as Canadian Sailcraft. It makes sense that the CS costs more as they were built to compete with higher end brands like Sabre & Tartan not Catalina or Hunter.
Our CS has been from South America to Newfoundland and everywhere in between and with with well over 30,000+ nm on her she shows little to no signs of wear or stress.
I've owned three Catalina's a 30, 36 & a 310 and they all began to creak and groan in winds over 25 knots. This is probably due to the lack of tabbing on the bulkheads that actually secure them to the hull and cabin top and in general the fact that they are built as coastal cruisers.
Our 1979 CS-36 has never made a peep and we've had her in 45 knots+ and 8 to 10 short steep seas. Under the previous owners she weathered many tropical storms including the remnants of two hurricanes..
If you can find a well kept CS-33 for anywhere near the price of a Catalina 30 buy it!
Having stated the above a C-30 is fine & more than adequately built for your intended use..
P.S. Raymond Wall designed the CS-33 and had previously been the chief designer for Camper & Nicholson in Europe before joining CS yachts in Canada. Camper & Nicholson's are very, very high quality boats (closer to Morris or Passport) designed to handle the rigors of the North Seas and are true blue water boats. Ray Wall designed the CS
line very similarly to the Camper & Nicholson
line in terms of layup and build construction.
With a Catalina you get in-house design, which is not bad for bay or coastal cruising but you don't get a highly regarded & pedigreed designer like Raymond Wall if you buy a Catalina. Ray Wall designed the CS boats to handle the worst yet still turn out good speed and still track straight!