I'm looking to purchase a dedicated server to use to resell web hosting space. I'm looking at WiredTree currently, and I see that 2TB monthly transfer and 10Mbps unmetered is the same price. I'm somewhat new to the idea of unmetered bandwidth. I can visualize and understand the quantity of 2TB of transfer, but I'm not able to really understand what 10Mbps would mean in real life terms.

I don't consider overselling any way to do business, I'd much rather underpromise and overdeliver than vis versa. The crux of my question here is, really, what sort of capability would that leave me with? It's easy to do the math for a monthly transfer rate and say xGB/month costs me y, and build plans around that. I'm not sure what 10Mbps really means though. Clearly I can't promise 5TB to 1500 users, but the other side is that I don't want to undersell my capability either. Can anyone enlighten me a bit here?

See the following quote to help you think of a clear number for the bandwidth. Please note I'm quoting this from another user that posted this 2 years ago.

10Mbps unmetered = ~3TB/month = ~100Gb/day
100Mbps = above values times 10

With 10Mbps unmetered your port will be limited to only 10Mbps though, so if you have a lot of people at peak times, this might cause your site to respond slowly. 10Mbps can only push about 1 Megabyte/sec, whereas 100Mbps can push 10x that.

100Mbps unmetered on the other hand is probably overkill though. If you value speed, I'd recommend buying more blocks of metered bandwidth until you really need 100Mbps unmetered.

Although the traffic itself doesn't have any limits, the unmetered port itself is valved at 10mbps. This means your server will be able to support up to 10mbps of traffic (uploads/downloads) at any given time. If you go over that you will see performance issues depending if the port is burstable to whatever amount. If you go for the dedicated bandwidth you'll likely release yourself from this limit but be limited with an actual amount of bandwidth.

I'd say that a 2TB data transfer limit with 100mbps connectivity would be better than 10mbps unmetered usage. In real life, you're not going to be able to squeeze that much more out of a 10mbps line anyway, and if you will be in the position to do so, it'll likely come at a performance cost during peak times.

2TB on 100Mbps is better than 10Mbps unmetered because you most likely will only get 'up to 2TB' from the 10Mbps link - however, for budgeting purposes, getting unmetered services ensures that you will not have to pay any excess charges for traffic - which can really add up if you are not actively monitoring a 100Mbps link.

Not speaking about WT specifically but you should keep in mind that many "unmetered" links are shared vs dedicated bandwidth. So while you can get over 3TB of bandwidth on an unmetered 10mbit connection it doesn't mean you will always be able to. Dedicated bandwidth is just that, it's all yours (IF you host is not overselling that is).

2TB on 100Mbps is better than 10Mbps unmetered because you most likely will only get 'up to 2TB' from the 10Mbps link - however, for budgeting purposes, getting unmetered services ensures that you will not have to pay any excess charges for traffic - which can really add up if you are not actively monitoring a 100Mbps link.

The chances are that an "unmetered" connection is shared among other servers as well so you may not even reliably get 10mbps - it depends on how the provider chooses to do things.

And 2TB is a freaking lot of transfer. All of my servers have had the 2TB transfer limit, and none of made it anywhere near close to that. The most any one server used was 800GB and that was because this guy had his software plugged on national TV which got him a crap ton of downloads.