Unless it's changed since I last played EVE, the EVE servers all reset every night so EVE is down for a reasonable time each day. In WoW the equivalent happens only once per week.

The WoW 'cross realm' zones are also the "instanced" zones so while they are cross realm they actually hold much less data and people than the single-realm parts. Even the 'cross realm' areas are still restricted to a "battle group" of realms of 5-6(?) realms.