Broadcom may make Tim Cook happier, but Atheros is more the "Steve" of wifi chips. However, the 2007 MBP uses Atheros - yours is actually a different issue.
I actually made myself a Broadcom airport card, for less than $20 and it's faultless. Atheros cards have always worked great for me too.
The only time I've ever had WiFi problems is under really really old versions of Ubuntu on a ThinkPad.
I suspect a lot of problems are caused by interference, or really densely populated areas. Even out here in the boonies of North Houston, there are 8 - 10 WiFi networks visible, neighbors etc.
Broadcom may make Tim Cook happier, but Atheros is more the "Steve" of wifi chips. However, the 2007 MBP uses Atheros - yours is actually a different issue.