Most Successful Shield member out of Dean Ambrose, Seth Rollins and Roman Reigns

Seth Rollins Wins the United States Championship after defeating John Cena at Summer Slam. With this victory Seth Rollins is now the first wrestler to hold the WWE Championship and the United States Championship at the same time.

Summer Slam was Set up to be a WWE Championship and United States Championship Match where the winner takes both Championships. Seth Rollins went into the match as the reigning WWE Champ and John Cena was the US Champ.

 Last Year the Shield (Dean Ambrose, Roman Reigns and Seth Rollins) broke up sending all three men onto there own Solo Careers. Dean was initially pegged a the successor and likely champion as he took on a leadership role early on in the shield. Dean also won the US title shortly after arriving and held it for one of the longest title reigns in history (300+). The leadership started to fall more evenly balanced as the group stayed together long. Roman didn't initially start as the highest member, in fact, he was probably the lowest on the totem pole when the Shield started. As the Shield started heading for separation it started to become apparent that Roman would be the guy WWE would lean on as the Top guy. Seth Rollins definitely was no slacker as a member of Shield. He was able to pull more than his share of the weight. Seth turned heel first and turned on the group to join Triple H and the Authority. Shortly after Seth won the money in the bank contract.
This year started with the power shifted. Roman Reigns won the Royal Rumble and secured a spot in the main event to Wrestle Mania defeated Daniel Bryan the following month and was unsuccessful at winning the Wrestle Mania match for the WWE title.
Dean Ambrose had a rocky year. After getting his ass beat several times by Bray Wyatt he competed in several senseless IC title matches including a match with Barrett that ended in a DQ and a 7 person ladder match which he did not win.
Seth year was good. He was doing great as a heel and he had his good old MITB brief case. Seth faced Cena and Lesnar in a triple threat match at the rumble an had an amazing performance. Seth later cashed in the MITB during the Wrestlemania main event between lesnar and reigns making it a triple threat and this time he was able to win the WWE Championship.
Now at Summer Slam we have a full year of the Shield Broken up and without a doubt Seth Rollins has left his former allies in the dust. Seth has held the WWE title since mania and has now made history as the WWE/US champ.

Notible stats

Dean Ambrose
US Champ for almost a year

Roman Reigns
2015 Royal Rumble Winner
WWE Tag team Champion
Victories over Randy Orton, Daniel Bryan and Bray Wyatt

Seth Rollins
WWE Champion and US Champion at the same time making history
Won main event of Wrestlemania 31
MITB winner
WWE Tag team champion
Victories over Dean Ambrose and John Cena

If you look at these stats Seth is clearly winning. Welp I guess Seth will get that statue.