The EotH has, on a per population basis, the best space units in the game. The Ascendancy Star Destroyers are only 3 pop, deal as much damage as ISDs, have more health+shields, and carry 4 very good fighter squadrons. EotH starfighters are fantastic, and are as good as NR fighters in dogfighting (especially the Nsiss and Scarsiss). However, their fighters don't carry torps like NR fighters do. The Syca bombers are very fast for bombers, which is helpful if you want to micro them.
Their Chaf Destroyers deal almost as much damage as VSDs, and are much tougher. Karieks right now cost only ONE pop, carry a squadron of fighters, and are great damage sinks with their power-to-shields ability. They're also very cheap for 1200 credits.
Another very unique and useful unit is the Nuruode broadside frigate. It has all of its guns (the equivalent of 69 megamasers or turbolasers) on one side. These can do a ton of damage if you jump them in and manuever them properly. They also carry a fighter squadron and are fairly cheap at 2000 credits.
And the Eoth also excels at hit and fades. Their Phalanx battlecruisers and Syndic destroyers do NOT have targetable engine hardpoints. The EotH also retreats much faster than the other factions (5 seconds instead of 10). You can jump in 4 or 5 of these capital ships, do a ton of damage, and get away really easily if the fight turns on you.
These benefits come with a downside. The EotH is a mobile force, few fixed defenses. No HVC or planetary Ion cannon. Their Brask stations are poorly armed but come with a LOT of fighters. This means that you shouldn't rely on defensive structures, but rather keep smaller fleets to garrison your flank. In addition, the EotH is a more expensive force than the other factions, but it's balanced somewhat by their starting position. A lot of their systems have pretty high credit values, and you can fill some of those systems with all mining facilities.
In land combat, their phalanx commandos are cheap and very useful. Their rapid-fire-tanks and Gilzaens make a great backbone of your army, especially for their costs. The Mortar tank has great range and is tougher than the other factions' artillery units. The megamaser tank is great, but it's also not as useful as you'd think, especially for its cost. I find that 3 Gilzaens (700 credits) are much better than a single MMT (1100 credits). The Airstraeker is a great air unit too, fast, and pretty powerful.Their rocket scouts are also fantastic. Unlike the IR's speeder bikes, the rocket scouts CAN capture build pads and landing zones. This makes them much much more useful. However, be warned, the pathfinding AI tends to do weird things with the rocket scouts. Keep an eye on them when moving long distances.
And lastly, one AWESOME thing about the EotH, as long as you hold Niruan, you get free intel on every visible system. By "visible" I mean every system that you've either been to, or opened a hyperspace lane to. The greyed out systems, you still can't see. The intel consists of all ground structures and fleet sizes, but not fleet compositions or land units. Still, it's very very helpful since it's basically completely free.
Hope your brother enjoys playing as the EotH, they're a ton of fun.