If you are playing a Downloadable MMO you start by downloading a large file the first time you play. After that, if the game ends up becoming popular, it is highly likely there will be continual development and the distribution of regular patches. This could mean frequent downloads of new content. This is good since it means you get more game to play, but the hassles can be frustrating sometimes. This is one thing you cannot skip, as a lot of gameplay features may not work on an outdated version. A new class of creatures – check. New maps and locations – check. Simply a couple of new items for your character – check.
Browser-based MMOs on the other hand have their negative points in terms of server issues. If the game is that popular, it would require a dedicated set of servers, which may not work all smoothly every time. Each new development may mean a downtime of a few hours.
Not all Browser-based MMOs are without good graphics (see the available image from Tribal Wars).
But those which have good graphics, may take time to load fully. Good examples of MMOs which have focus on the graphics are – Habbo Hotel, Renaissance Kingdoms, Fallen Sword, and Tribal Wars. Habbo Hotel incidentally, is famous for its dynamic graphics.
Now it’s up to you to decide what kind of MMO game you want to play. The choice is yours.
(Images taken from the respective game sites)