The three main benefits are performance, reliability and monitoring.
Performance As I describe elsewhere in the thread I am not doing VPS virtualization, I am not masking I/O, I am not tossing as many users as I can sell on each machine. Once I perform bandwidth aggregation, I can have more users per server with less I/O and the prices will drop. That is why I'm not saying beta customers have fixed prices, they have a fixed discount. I expect my prices to go down once I implement MT4 specific optimizations - and a VPS will never have those shared with other VPS (it violates the model). I have been wrestling with the idea of offering a "sardine" service similar to the VPS on a separate machine, where I add as many users as the machine will hold. I would price that service around $8-12/month and it would exist on a separate machine only. The "sardine service" may be popular, but I don't think it would be worth one late trade per month.
Reliability VPS servers offer server reliability, but this doesn't always translate into application reliability. We are focused solely on MetaTrader4 and making the application stay up all of the time it is scheduled for. If MetaTrader crashes or is unresponsive, we load it back up again. There are ways with VPS in the Operating System to load MT4 each time the server restarts, but checking for frozen applications and crashes is application specific code.
Monitoring As mentioned above, we will inspect the process for all three levels of service to make sure it is running.
At the second level of service and above, if MetaTrader hangs and or quotes stop coming in, we will use automatic means of solving the problem when possible. If they are not successful, my cellphone will be alerted to the problem and it will be resolved.
We will inspect the EA logs for error messages and handle them appropriate to the error code. If your EA keeps sending invalid trades, we will do as you request - stop the EA, contact you by phone or email, ignore the error, close MetaTrader, restart MetaTrader or (paid by the hour) debug the application.
We will also offer advanced logging options to be included in the EA, so the EA tells us what is going on. The MetaTrader logs will also be monitored. Both the EA logs and MetaTrader logs will be available with filter options on the website. We also hope to provide weekly performance reports available on the website and through email if desired but this isn't a feature we have tested.

I think those are the main differences in technologies. We are also offering backbone connected systems for minimal latency (which will vary on VPS to VPS provider) and we might be able to offer *application level* uptime guarantees while datacenters only offer network guarantees and VPS systems would only offer OS level guarantees. My previous testing of VPS found that it was unsuitable for my needs since it added a 1/3 to 2/3 of a second application latency. That may or may not be true of the VPS services listed above or found other places. I'm running the applications as native to the kernel, with libraries translating calls to the kernel. Each application exists in separate user space. I can also put a "jail" around the application but I don't think this is necessary or desirable.

Honestly, I am building this system for me to use. I have... very high goals. I'm hoping to #1 *reliably* run in stealth mode so the broker won't see my profit or SL levels. Look at http://www.forex-tsd.com/65001-post41.html and notice the difference. The brokers are known for manipulating the datastreams of their clients to hit SL and TP. This is an Advertised FEATURE of MetaTrader http://www.metaquotes.net/manager "analyzing aggregate positions of clients and managing your own company's positions;" with "sending quotations to the general dataflow on the server;"
#2 I'm hoping to (after a month or three of development work) write an EA that reads the level 2 datastream from the banks and process it before the broker does. If I see a big spike from the banks, I place an order from the broker. This is only possible if I have absolutely the best connection - so that is what I'm buying for myself. I don't need *absolutely best* for stealth mode, but I do for "racing the bank".

I hope that clarifies my motivation - I am not trying to set up a Metatrader hosting empire, I'm trying to get high quality at affordable prices. The reason I picked 6 people maximum for beta is that it allows me to break even on monthly costs. 5 slots left.