Why not both?
In a game jam game, particularly one with ratings that are not from a panel of judges, you want to make it as easy as possible for everyone to play your game the way they want to.
For Glitcheon (https://river-forge-games.itch.io/glitcheon) we have had almost 800 browser plays, and 40 downloads (for windows which has been available since submission).
By our specific case you can see that the browser build is most valuable, while there is still some value in releasing it for download as well.
In most cases if you've made your game WebGL compatible you won't have much if any problems porting to windows, linux, and mac.