Many consider the 1.7.10 PVP system to be the best. The Combat Update of 1.9 split the PVP community into two large groups, consisting of the 1.9+ group and the 1.8 and below the group. However, within the 1.8 and below group, many choose 1.7.10 over 1.8.9 because 1.7.10 has better block hitting animations than 1.8.9, compatible with drinking or hitting the ground .........only difference I know of is that 1.7 has better hit registration. If you're playing a 1.7/1.8 server on a 1.8 client, you'll be at a disadvantage against players on 1.7 clients