The best way to get a real feel for this, is to take your standard nuke and hit a D village with a 20k/20k spear/sword Defense w/ a lv20 wall in the simulator.
See what that looks like in terms of wall loss and also in terms of troop loss between ram lv1 and lv3. Play with it a bit and modify the ram #s, while keeping the pop for your troop count the same. ie keep it at say a 21000 troop population.
Play with the defense a bit also increase it if u want and you will definitely start seeing the advantages once you start hitting higher stacked villages with more troops in them.
Keep in mind you will be sending other nukes in behind and the more the wall gets dropped at the start the less troops you may have to lose on the following hits. When people have the defenses to stack vills understanding this is going to help you.
A complete guide to rams amongst other things. just scroll down a bit and read I think its like the 8th spoiler down in the list.
http://forum.tribalwars.net/showthread.php?t=199781
I'll copy paste
cheesasaurus little post on techs for people.
Researching a level 1 unit allows you to train it. So, if you want to make light cavalry, then you would have to research level 1 light cavalry in the smithy before you can start actually training them in the stables. That's one reason to research something.
Some worlds have multiple tech levels. Researching higher levels will make your units stronger. Later down the road, this makes a very big difference. That's why it costs so much to research higher levels.
For 3-tech worlds:
level 2 units are 25% stronger than level 1 units.
level 3 units are 12% stronger than level 2 units.
400 level 2 axes are just as strong as 500 level 1 axes, and only take 4/5 as much time to train.
The costs of the research quadruples every time you raise a level, but the cost to train the unit remains the same.
Knowing this, you can figure out when you want to upgrade your units.
For example, it's cheaper to make 236 level 2 axemen than 295 level 1 axemen, and they have about the same fighting abilities.
For 10-tech worlds:
Every upgrade makes your units 4.608% stronger.
The costs of each research is 60% higher than the previous level's research cost.