There is one big difference. The DNC is trying to ensure Hillary gets elected. The RNC is trying to ensure that Trump doesn’t get elected.
Blocking Trump is just the first step of the RNC's agenda. The second stage will be thanking Cruz for his service, telling him to step aside along with by-law 40, and nominating their candidate of choice (Jeb Bush or someone similar). So it's a more meandering path than the DNC's coronation of Hillary (the GOP doesn't have as many unpledged delegates, so they need to get creative), but same principle.