I much prefer the new system. Yes the the logic behind it is the same (an elo number assinged to you) but the user experience is much better now imo! Bear in mind that does not mean the gameplay; trolls, afkers etc. That is unrelated. I'm referring to the system of ranking.
Before, we simply had a number to represent our skill level/placement within the league. The number would rise and fall in increments and the only goal you could ever really have was making it go up, but there were never any milestones and achievements to satisfy you along the way.
Now I feel like I have a much better bearing of how I fit within the league, how I can move up and down and measure my performance and achievements with tiers, divisions and leagues, whatever they're called!
For example, I started in Bronze I and fought my way into Silver V. I'm now trying for the 3rd time to get into Silver IV. Each time I get closer to the promo series and into the promo series it is a HUGE DEAL and adds a lot of pressure/stress/excitement to the experience. I feel like I'm gunning for something and when I get it, it is massively satisfying.
For all I know if this was Season 2 I may have gained +100 elo as the equivalent and that's that. All of sudden that's not very exciting is it.