You'd be amazed how small a difference 64-bit makes in browsers. And in most apps for that matter.
Source: I package apps for portable use for PortableApps.com. We analyze many of our apps for whether the trade-off of a size increase including both the 32-bit and 64-bit versions of an app is outweighed by the performance or stability advantages of the 64-bit version of a given app. Including the 64-bit version is worth it in VERY few instances. Even then, it won't help most users.
Source: I package apps for portable use for PortableApps.com. We analyze many of our apps for whether the trade-off of a size increase including both the 32-bit and 64-bit versions of an app is outweighed by the performance or stability advantages of the 64-bit version of a given app. Including the 64-bit version is worth it in VERY few instances. Even then, it won't help most users.