At 24 points, Motti is the least expensive of the Imperial options. His boost is to give all ships greater hull value based on their size - small ships get 1 hull, medium get 2, and large (not out yet) get 3. With the current Imperial ships, that means Gladiators get 1 hull (5 to 6) and Victorys get 2 hull (8 to 10!). The biggest benefit then is to the Victory, which makes them far and away the tankiest ship in the game - few oppenents are going to be able to throw enough dice to strip through all your shields (and redirect tokens) and land 10 hits on your hull. Motti goes well with a few high HP ships, working to protect your investment in your larger craft. When Imperial Star Destroyers come out, Motti will work even better - adding 3 hull to the largest ship in your fleet.
Admiral Screed comes in just 2 points higher than Motti, at 26 total points. Screed's benefit is that once per activation (not per attack), when a friendly ship is attacking, it may spend 1 die to change a die to a face with a "crit" icon. Screed loves black dice - he can change one black dice being rolled to a hit / crit combo, which means 2 extra damage on 2 blank die. Factor in Advanced Concussion Missles and it turns into 4 extra damage on 2 blank die. Remember, you have to pay a die to change a die, but even in a situation where you have rolled all hits, that is still a free crit with no loss of damage.
Screed wants those black dice, which means he wants to command ships that throw them. Either Gladiator class ship or the Victory I are his best places to be, and with the Gladiator's mobility, you'd be more likely to throw the dice in question. Screed is the lynchpin of 3 Gladiator builds, and works perfectly well in a list with a mix of Victory I's and Gladiators as well.
His drwaback though, is that he is much less usueful with Blue dice. All Blue sides have a positive outcome of some sort, so unless you roll a massive number of accuracies with your blues, and your reds, you are pretty much never going to be adding net damage to your roll.
Grand Moff Tarkin
Tarkin solves one of the biggest Imperial problems - because you have such a high command value, you aren't particularly able to adapt to chnages on the board - you need to plan ahead a turn or two to make sure your commands will match with what your ships need to do. In addition, you have room to stock away 2 or 3 command tokens, but unless you spend the first few rounds saving tokens, you'll never get enough. Tarken solves both these problems. For 38 points, 14 more than Motti and 12 more than Screed, you get, at the beginning of each ship phase, 1 command token of a single type given to each one of your ships.
This can be useful for anything - a token to bank for later in the first round, a much needed navigate to slow down, or speed away, a free squadron activation from each of your ships, hasty repairs for a ship you didn't think was going to be the focus of each enemy attack (and a banked token for the rest). Tarkin, for those 14 extra points, represents a degree of flexability that the Imperial Fleet normally cannot utilize, and a chance for overwhelming boosts if that flexability is unneeded. Tarkin gets the most bang for his buck flying with Victorys - their 3 Command Value means that he can stock more tokens in the early rounds, and help them be more responsive in later rounds. He can also work wonders with a pack of Engine Tech Gladiators as well, giving them all a free Maneuver token each round, leaving them free to dial up firepower or repairs on their command dial instead.
The cost is his biggest drawback though. 14 points more than Admiral Motti makes him the most expensive upgrade on the Imperial side you can possibly field. His base cost of 38 means that he is priced the same as a rebel Corvette. For the level of benefits he gives you, he costs just under 13% of your 300pt list - or 5% of your list compared to Motti. And to maximize the investment you get out of taking him, you want a large number of ships on the board.
That's it for Imperial Commanders at the current time. Next time we will look at the Rebel Commanders and how they should be used.