1st: Make sure it's the Silent Pro "Gold" M1000w, the standard Silent Pro 1000w is Bronze certified, not gold...
The V is fully modular (so 24 pin and 8 pin CPU are removable) and the silent pro gold isn't fully modular (24 pin, 8pin and 2 PCI-e are not removable)
i would look at the cable you need and then choose the one with the cable i need (if you want to SLI or not, PCI-e will be important, etc...)
From what i've seen, they're surely same internals but wired differently as this test http://www.kitguru.net/components/power-supplies/zardon/cooler-master-v-series-1000w-psu-review/6/ overload the V-1000 to 1192w and the M1000 is 1200w Peak too so...
It only depends on price (grab the cheaper) and/or if you need specific...