To his case, vps will fail.
And in everyone's case it will also fail.
I've experienced downtime with like 4 different companies, due to ddos attacks on other local vpses.
I have a huge experience on this.
Buy a dedicated and you will be fine.
I'd recommend vrtservers.net (If you don't have ddos attacks, if you do, they'll ban you, so backup daily), their connection is good, price is awesome, etc. But they do not have tollerance.
ps : Using limestone right now. they just ROCK. (Not that cheap, but I've had 2 ddos attacks and they didn't close my account)