I have really enjoyed both ER2s... I initially struggled to understand their positioning, given how close the price is to ER3 (and how close the ER3 sound to the 4!).
While the 3 are a cheaper alternative to the 4, I would say the 2 is more a COMPLIMENTARY device to the 3/4.
The dynamic drivers certainly have a different texture, while maintaining the overall Ety profile. The ER4 has tighter refinement, the sounds are sharper more dileneated, whereas the 2 is softer and blended. I overall prefer the transparency of the BA myself, but it is a lovely contrast between the two (and certainly a good choice for those that prefer dynamic!).
The other big difference is the 2's are a little harder to drive (still very easy!), and also are both a little more sensitive to seal. The ER2XR is the bassiest Ety but also with the venting is trickier for me to get a good seal - I ended up switching to the larger tripple flange in my left ear to compensate.
If you are looking to experience Ety on a budget, I still feel the ER3 is more representative. Those who dislike BA, or want to add some variety to their Ety stable will be VERY happy with either ER2.