Currently most of the telco in the market offers mobile data services. Some telcos brand it as mobile broadband, HSPA, etc.
Basically the service you purchase is mobile data service. Whether or you are camped on 2G or 3G depends on your handset capability.
If you are using the old 2G phone, you will use GPRS/EGPRS to access the data service.
If you are using the 3G phone, you will use 3G/WCDMA to access.
If you are using the 3G with HSDPA capable phone, you will use HSDPA to access.
GPRS/EGPRS ~ 12kbps to 59kbps depending on phone model
3G/WCDMA ~ 384kbps
3G/HSDPA/HSPA ~ 1.8Mbps to 7.2Mbps depending on phone model
To make things simple, what you as a subscriber should care is just the pricing of the plan.
For example, 1010 offers $168 for 100MB, $568 for unlimited.
There are too many plans with different bundles. So you just need to make the comparison based on your need.
If you just want to do some browsing on your mobile while commuting, I think 100MB or 150MB is more than enough for you to use. However, you have to bear in mind that if you use more than what you subscribed, you will be charged at $2/MB!