The Vickers was a fairly heavy weapon that was better suited to defence where as the Lewis Gun was a bit lighter and was used both on the ground and mounted to British aircraft.
The Vicker's was water cooled which can present problems if the water boiled off where as the Lewis was air cooled.
The Vickers MG's were the British main defence gun in the trenches that had a range of around 3700yds approximately firing a .303 bullet. Used in defence with interlocking fields of fire they were absolutely deadly. Here's some info on the Mk.1 Vickers.
Method of Feed Fabric belt from right side
Belt Capacity - 250 rounds.
Construction - canvas with brass separating strips
Weight Empty - 30 lbs.
With water - 40 lbs. (approx.)
Length 3 ft., 7½ in.
Barrel Length - 28.4 in.
Calibre - .303-in.
Rifling - number of grooves - 5; twist - 1 turn in 10 in.; direction - to the left; depth - .005 in. to .008 in.; width of lands - .0936 in.
Sights Type - aperture and blade.
Range adjustment - using Plate, Graduated, Tangent Sight, No. 2 Mk. 1 for Mk. 7 ammunition - 100 to 2900 yd.
Range adjustment - using Plate, Graduated, Tangent Sight, No. 2 Mk. 2 for Mk. 8z ammunition - 100 to 3700 yd.
Sight base - (radius) - 36 in. (approx.)
Cyclic rate of fire 450 to 550 rounds per minute.
Method of breech locking Toggle joint.
System of operation Recoil, gas assisted.
Change lever Nil - full automatic only.
Type of cooling Liquid cooling
Capacity of barrel casing 7 pints (approx.)
Number of rounds required to boil water 600 (continuous firing)
Rate of evaporation 1.5 pints per 1000 rounds
Ammunition Cartridges, S.A. Ball, .303 in., Mk. 7, Mk. 7z or Mk. 8z, or Tracer or A.P.
The Lewis gun was used in both ground and air defence and it also fired a .303 bullet.
Type: Light machine gun
Country of Origin: United States & United Kingdom
In Service: 1914-1953
Designer: Samuel McClean & Colonel Isaac Newton Lewis
Birmingham Small Arms Co.
Savage Arms Co.
Light Infantry Pattern
Model 15: 28 pounds (13 kg)
Mks I-V, Aircraft Pattern: 16.975 lb (7.7 kg)
Length: 50.5 inches (1,280 mm)
Barrel Length: 26.5 inches (670 mm)
Width: 4.5 inches (110 mm)
Cartridge: 0.303 British .30-06 Springfield
Action: Gas operated
Rate of Fire: 500-600 rpm
Muzzle Velocity: 2,440 feet per second (740 m/s)
Effective Range: 880 yards (800 m)
Maximum Range: 3,500 yards (3,200 m)
Cooling Systm: Air Cooled
Feed System: 47 or 97-round drum magazine
Sights: Blade and Tangent Leaf