You can't buy the EX3 costumes. They are given out via events that you have to participate in and you only get ONE per event.
And the EX3 ones look crappy on purpose. They're supposed to look like the PS1 graphics of the original games. Leon, Ada, Chris and Sherry even get their costumes from RE1/RE2. It's not minimal effort, it's a design choice for fans of the series since the 90's. It's for nostalgia.
But regardless, you can't get them, so that decides for you.
Even if EX 3 can be unlocked with ponits and tickets, at the rate they are giving out tickets, I wonder if it might not be a bad idea to purchase EX 2 with points I have and just save the tickets for EX 3. Also makes me wonder if I'll be able to unlock EX 2 with tickets.