Why is there a very different speed to two neighboring VPS?

Question

network hardware

There are 2 VPS in one distant city from two different companies. Both have great speed. But here the speed from me to one of them rests on the provider's limit, and to the other - three times lower. Support did not help, they say everything works. An attempt to do a traceroute produces a string of unresolved hosts.
Question: can I try to somehow influence this all, or will I have to throw out this VPS? If yes, tell me what to google.