We're just got back from Westin Los Cabos. We own two EOYs at Lagunamar. Yes, Lagunamar is a fun resort and being right across the street from the busy outdoor mall adds to the festiveness of the area. There's always something to do in walking distance! I don't know the Westin Cancun but if the beach is swimmer friendly and their pools are inviting, and you're looking for a 3-bedroom because of kids in your group, that might be a good choice because of ocean access for swimming. You could catch the city bus and use it easily to get to other 'hotel zone' areas. I agree with other comments that Westin Los Cabos's beach is NOT available to swimming - stronger surf and rocky areas. Their pools are very lovely, but no slide like Lagunamar. There are ping pong tables, pool tables (in the sports bar), oversized chess board; a miniature putting green of 9 holes; tennis courts (w/pickleball paddles available). Their activity chart is filled with young and adult things to do. You have to Uber (or use your rental car) to get anywhere. This is our first time and we are using Uber which has been VERY easy! We actually have been very pleased with Los Cabos - staff great; food good! Views and setting spectacular. But I'd say it's more laid back and more easy-going than Cancun. Side note: if this is a for a family w/kids, be sure to get the 3-bedroom that's in the main Cabo resort, not Baja Point. Baja Point is separate (with one pool) and requires a walk to get to the main resort where all the activities occur. Good luck! Either decision will be enjoyable and memorable!