Much more powerful, much faster, more accurate, more variations in armament but possibly less armored.
WW1 saw the very first deployment of tanks, and, as such, they should be considered prototypes, and were barely functional in practical, operational sense. Even the most advanced tank in 1918 was barely useful; by the standards of the time, they had very little armor protection, were extremely slow, and hideously mechanically unreliable (most broke down after only a couple of miles).
Tanks in WW1 had thin armor - generally, proof against rifles, but often, not even machineguns. Large-caliber (.40 or .50 caliber or 10mm+) anti-tank rifles were quickly development, and were effective at penetrating virtually all tank armor at ranges up to 100 yards. Tank armor, of course, was completely insufficient against any form of artillery.
Likewise, they were hideous overweight, and underpowered by the weak engines of the time. The treads were cantankerous, prone to breaking, and the suspension systems were extremely primitive. Consequently, speeds were ridiculously slow - only a few mph (most men could outrun a WW1 tank).
When compared to a tank produced during WW2 (for example, the German Panther, the US M4 Sherman, or the British Churchill), here are the major differences:
- Speed - even the slowest tanks in WW2 generally could attain at least 20 mph, compared to the 4-5 mph of most WW1 tanks
- Maintenance - few WW1 tanks could travel more than 10 miles before breaking down, and they were all horribly difficult to perform maintenance on. In contrast, most WW2 tanks could travel several hundred miles before breakdowns, and were designed for much simpler maintenance.
- Track and Suspension systems - the track-over-rollers system common to all WW2 (and later) tanks was only just being developed in WW1, and the concepts of torsion-bar or hydropnematic suspension were years away. Better tracks and suspensions lead to far superior cross-country and obstacle traversal at much higher speeds.
- Turrets - using a single turret for placement of armaments was highly unusual in WW1. By WW2, all tanks used a moveable turrent, or were considered "mobile artillery" if they used fixed armament. The innovation of the turret provided a much more useful vehicle than the fixed-field-of-fire that most WW1 tanks had.
- Crew - instead of the typical 6-10 people inside a WW1 tank, WW2 tanks seldom had more than 5.
- Armor layout and amounts - armor improved radically, with much higher quality steel being used in WW2 tanks, and thickness of the armor went from a couple of mm to up 10cm or more. Overall protection of the tank was very significantly upgraded with the advent of the concept of sloped armor, too. Overall, while a WW1 tank could reliably be penetrated by heavy caliber rifles, most WW2 tanks were protected against all small arms and light field artillery, and many were immune to anything except super-heavy artillery fire.
- Armament - WW1 tanks tended to carry a mishmash of armaments, from machineguns to light cannons, to heavier cannons. Typical armaments were 2-3 cannons, and 6+ machineguns. In no case did cannons go about about 40mm (or 10-pounder) in size. Contrast this to WW2, where (most) tanks mounted a single high-caliber cannon (70mm or bigger) and 2 machineguns.
- Powerplant - the very basic, noisy, unreliable petrol-using inline piston engine of WW1 tanks gave way to mostly diesel V-aligned engines of WW2 (though the M4 Sherman is a notable exception, using a radial petrol engine). The result was a much, much more powerful engine in a smaller space, with a very high reliability factor, and significantly better fuel consumption. Typical WW2 tanks had between 4 and 10 times the HP of a WW1 tank, and generally had between 50-100 times the power:weight ratiOS of their WW1 predecessors.
- Better internals - the internal layouts of WW2 tanks were better arranged, for higher crew comfort (with a notable exception of the T-34), better crew protection, and the addition of radiOS and optical rangefinder sights.
Modern generation tanks continued this trend, with better armor, higher power engines, more powerful guns, and improved electronics, but the modern tank is not radically different in design than a WW2 tank, whereas the differences between a WW2 and a WW1 tank are vast.
