r1 is not easier by default like many sometimes claim, but there are breakpoints. Note that this is just for r1.
R1 changes the following from elite:
Players deal only 76.9% normal damage (so, -23.1%)
Enemies deal 20% more damage
Enemy saves go up by 1.5 / skull
Healing during combat reduces to 40% (so, -60%)
Crowd Control duration reduced to 44% or 6 seconds, whichever is higher (-56%)
Death Timer 6 seconds
Reapers can spawn (basic 4 only)
Higher tier champions
Lost Souls can spawn (restores your SP by an amount based on skull level)
Reaper trees give you bonuses. These bonuses can eventually mitigate some/all of the above penalties.
I did the math a while back, so I'm going by memory right now... but for damage it takes around 32-36 reaper points in your respective reaper tree to theoretically match the damage penalty of r1 (assuming no other multipliers. The stronger you are, the less this helps, but at the same time the stronger you are the less the initial penalty will matter as well. If an enemy has 5000 HP and you do 10000 damage outside of reaper, reducing it to 7,690 damage inside reaper is still one shotting it. the +44 extra universal spell power at 34 points is huge if you only have 100 spell power to start with, insignificant if you have 1000+ to begin with)
For DCs, it only takes 6 points all going to boost your DCs and main stat to overcome the enemies increased saves. Instakills don't care how many HP the enemy has. This is the biggest thing many people gloss over. Attacks land more often, thus you do better damage more often, or simply bypass HP by instakilling everything more easily.
For defences, it gets more nebulous and complicated as there are small boosts to prr/mrr, dodge, saves, as well as the HP boosts vs what your character has outside of r1.
So in general (and ignoring some harder to parse factors like lost souls, reapers, champion abilities, etc), elite is technically and mathematically easier than r1 until you have accumulated 30-40+ reaper points, then mathematically it starts to become easier.
However, this is only for r1. The reaper scaling continues with more skulls, where as the reaper trees/points can only do so much.
I wish more people who make the claim that r1 is easier would temper that claim with "when you have X reaper points". So many come from the perspective of maxed reaper points even when talking to new players with zero reaper points, and it makes things painful, awkward, and unfun for the new (to reaper) player.