Pro Leisurely real time combat
The large scale of the game controlling fleets in may solar systems allows for a leisurely pace to play, which makes for worthwhile way of controlling ones ships across multiple places. This makes for less stress in the game due to how intuitive and evenly paced the game is.
Pro Diplomacy used in a smart way
Different factions will send you quests that may effect your relationship with other factions meaning you will have to choose who best to make a friend or make an enemy when taking these missions. This bit of strategy can greatly change the outcome of a game depending on how well you have chosen who to help and who to possibly make angry.
Pro Large scale space combat
Sins games range from 7-130+ planets and hundreds of ships per player, all in real time, giving the game a fairly unique scale. Battles can wage on multiple worlds simultaneously and thanks to Sins UI and unit AI you can successfully manage fighting major battles, keeping your economy and ship production rolling, and development and research all at once (with some practice of course).
Pro Very distinct races
The game has three main races - Vasari, Advent and TEC and they offer completely different playstyles. TEC have the best economy, Advent's strength lies in their abilities and how they can be synergised and Vasari focuses on their tech - the incredible Orkulus starbase and Warp Stabilization.
Con Steep learning curve can deter casual players
While the game is one of the slower Real-Time Strategy titles, there is a huge learning curve that can wreak havoc on fledgling players. With some research required in order to colonize certain planets, researching use of larger fleet and capital ship sizes, to maintaining a thriving economic civilization, it will take many, many matches before players feel knowledgeable and skilled enough to play on larger maps or even against more difficult AI. With no true Single Player to speak of and little way of help in terms of tutorials, you must play in order to learn, sometimes using trial and error as a way of making progress.
Con Slow-paced logistics and combat necessitates situational awareness
Sins of a Solar Empire: Rebellion is a strategy title on a massive scale, with players able to colonize multiple solar systems in any given match. Due in part to this scale, there is a perceived slowdown in gameplay; lengthy building construction, minutes-long research and slow unit movement. While the game, at its heart, does appear to be slow (and sometimes is), awareness of your surroundings is paramount. With fleets sometimes taking minutes to arrive at a destination, and defensive structures quickly falling to a massive fleet, it is easy for players to move out of position allowing key worlds to become targeted and lost in enemy incursions if they expand too quickly. However, not expanding quickly enough can halt the player from building up a fleet capable of taking on an enemy, or pirates head-on. In essence, you must learn to balance fleet needs, knowing the right time to expand, while keeping large groups of your ships scattered in key positions to await reinforcements should the need arise.