The Douglas A-26 didn't become designated B-26 until after the Martin B-26 was out of service. The A-26 also has the distinction of being in service through three wars. WWII, Korea and Viet Nam and some surviving aircraft currently serve as fire bombers.
Since Douglas was already producing the A-20, they were able to incorporate a number of the Havoc's weapon platforms to the Invader's design. As you can see in the specs, it was a fast machine, could handle a load, all with great range. The pilots that flew it always commented on it's positive handling.
Douglas A-26 Invader specs:
Crew: 3
Length: 50 ft 0 in (15.24 m)
Wingspan: 70 ft 0 in (21.34 m)
Height: 18 ft 3 in (5.64 m)
Wing area: 540 ft² (50 m²)
Empty weight: 22,850 lb (10,365 kg)
Loaded weight: 27,600 lb (12,519 kg)
Max takeoff weight: 35,000 lb (15,900 kg)
Powerplant: 2× Pratt Whitney R-2800-27 "Double Wasp" radials, 2,000 hp (1,500 kW) each
Performance
Maximum speed: 355 mph (308 knots, 570 km/h)
Range: 1,400 mi (1,200 nm, 2,300 km)
Service ceiling 22,000 ft (6,700 m)
Rate of climb: 1,250 ft/min (6.4 m/s)
Wing loading: 51 lb/ft² (250 kg/m²)
Power/mass: 0.145 hp/lb (108 W/kg)
Armament
Guns:
6× 0.50 in (12.7 mm) M2 Browning machine guns in the nose
8× 0.50 in M2 machine guns in four optional underwing pods
2× 0.50 in M2 machine guns in remote-controlled dorsal turret
2× 0.50 in M2 machine guns in remote-controlled ventral turret
Bombs:
6,000 lb (2,700 kg) - 4,000 lb in the bomb bay plus 2,000 lb external on the wings
Douglas A-20 Havoc specs:
Crew: 2-3
Length: 47 ft 11 in (14.63 m)
Wingspan: 61 ft 4 in (18.69 m)
Height: 17 ft 7 in (5.36 m)
Wing area: 465 ft² (43.2 m²)
Empty weight: 15,051 lb (6,827 kg)
Loaded weight: 27,200 lb ()
Max takeoff weight: 20,320 lb (9,215 kg)
Powerplant: 2× Wright R-2600-A5B "Double Cyclone" radial engines, 1,700 hp (1,200 kW) each
Performance
Maximum speed: 339 mph (295 knots, 546 km/h) at 10,000 ft (3,050 m)
Range: 1,050 mi (912 nm, 1,690 km)
Service ceiling 23,700 ft (7,225 m)
Rate of climb: 2,000 ft/min (10.2 m/s)
Armament
Guns:
4× fixed 0.303 in (7.7 mm) Browning machine guns in the nose
2× flexible 0.303 in Browning machine guns, mounted dorsally
1× flexible 0.303 in Vickers K machine gun, mounted ventrally
Bombs:
4,000 lb (1,900 kg)
Martin B-26 Marauder specs:
Crew: 7: 2 pilots, bombardier, navigator/radio operator, 3 gunners
Length: 58 ft 3 in (17.8 m)
Wingspan: 71 ft 0 in (21.65 m)
Height: 21 ft 6 in (6.55 m)
Wing area: 658 ft² (61.1 m²)
Empty weight: 24,000 lb (11,000 kg)
Loaded weight: 37,000 lb (17,000 kg)
Powerplant: 2× Pratt Whitney R-2800-43 radial engines, 1,900 hp (1,400 kW) each
Performance
Maximum speed: 287 mph (250 knots, 460 km/h) at 5,000 ft (1,500 m)
Cruise speed: 216 mph (188 knots, 358 km/h)
Landing speed: 104 mph (90 knots, 167 km/h))
Combat radius: 999 nm (1,150 mi, 1,850 km)
Ferry range: 2,480 nm (2,850 mi, 4,590 km)
Service ceiling 21,000 ft (6,400 m)
Wing loading: 46.4 lb/ft² (228 kg/m²)
Power/mass: 0.10 hp/lb (170 W/kg)
Armament
Guns:
12× .50 in (12.7 mm) Colt-Browning machine guns
Bombs:
4,000 lb (1,800 kg)