The speed will depend more on the mobile operators coverage rather than the phone and laptop when tethering. If you have 4G and in some cases dual cell 3G you should be fine for most browsing needs.

Just be careful if you have a data limit as you will go through it a lot quicker browsing on a laoptop as a lot of websites compress information via mobile browsing. Porn would be a great way to blast through your packages fairly quickly, so I hear ...