If you are happy with the answer from the tabletop game, there we can have a clear winner:
Without looking for details, each model in the WH40k is described as having a certain "power rating" as well as a "point value", which offers a bit better granularity showing how "good" a given unit is. For example, a squad of 4 Space Marines Intercessors with a sergeant has a power level 5 and a base cost of 20 points per unit (which can be modified by adding equipment), while a squad of 10 Gretchin has a power level 2 with a cost of 5 points each.
So now let's look at Leman Russ:
As you can see, a single tank has a power level of 10 and cost 140 points.
Now, let's look at the Land Raider:
It has a power level of 15 and cost 285 points, but part of it might come from the fact, that a Land Raider is considered also as a transport unit. If you'd want to look at a pure tank, such as Predator (8/120), you could see that Russ has a certain advantage. Still, the Raider has stronger armour and more powerful offensive capabilities.
But if we consider a Baneblade Heavy Tank, we can see that it is a clear winner:
However, this is because the Baneblade is in a completely different category of units than Russ and Land Raider which is called "Lords of War" and it is reserved for either super-heavy units or super-powerful heroes (for example, Space Marines have a super-heavy tank called Astraeus, which is even more powerful than Baneblade, with power level 35 and cost 675 points).
Leman Russ tanks are relatively cheap and mass-produced on a story level, used in great numbers as an "armoured fist" smashing through the enemy. In contrast, both Land Raiders and Baneblades are treated with the utmost respect as artefacts.
Note: I'm not sure are those values current, but this was the closest info that I've found for the 9th edition of WH 40k
EDIT: I've found quite a detailed analysis (from a modern point of view) of WH40k tanks:
It is a slow (35/21 km/h on/off-road) but heavily armoured tank with a huge profile. It required 6 men to work in an extremely cramped place (with only 3 escape routes!) and operate very powerful guns which would be better placed on a static platform. Comparing it to real-life tanks would be fairly useless even before WW II, but it still works well as a mobile defence platform (the famous Guard "hold the line!") or to support the waves of expendable infantry. But it is cheap, easy to build and very customisable.
In comparison, to the previous tank, this is a masterpiece: it requires only two Marines to operate, as the rest is controlled by a powerful Machine Spirit (which can even control the tank autonomously). It is very fast (55/48 km/h) beating even modern Leopards, even while it is much heavier than them. It is covered with a special composite material that is much tougher than steel. The flip side is of course the cost: Land Raider would be very, very pricey to build. But it seems that it is well-designed to do what it is supposed to do: manoeuvre itself into a good position, smash through an unsuspecting enemy and deliver its real payload: Space Marines.
It is an incredibly huge (316 tonnes!) and therefore slow (25/18 km/h) tank, requiring 10 people to operate. Its armament is truly amazing, and the main cannon is inspired by a howitzer designed to destroy bunkers... but in the WH40k it shoots guided missiles. And it is just one (or two) of the "eleven barrels of hell!" However, Baneblade suffers from poor armour, and its speed and poor manoeuvrability mean that it requires solid support from other units to be effective in combat.