statica route table or iptables for VPS routing?

Question

iptables

The question is. There are several network interfaces and the standard route table with routes is now used. There are many VPS's on this server. How Zen is correct:
route table and end-to-end routing of these VPSs to the world?
or routing according to iptables rules?
In the first case, the VPS goes to the Internet along the route:
iptables [NAT POSTROUTE Masquerade/Source] - Static Route table
In the second:
Only iptables [NAT POSTROUTE Source] ignoring the static Route table, but the truth becomes more rules. More precisely somewhere 150 rules on POSTROUTE. Now 5 basic rules decide everything.
The question arose due to the fact that sometimes it is required to change the routing dramatically with a script, let's say send Internet traffic through a different interface. And either drop static routes and overwrite (route), or drop iptables and overwrite the rules there.
Now:
300Mbps channel load, 78 static routes per route, 5 interfaces