|Quoting Okcflyer (Reply 199):|
In terms of weight, see the below from Wikipedia. I haven't seen empty weights yet but the delta should be in the 5-6-7% range in favor of E2.
Maximum takeoff weight 56,900 kg (125,400 lb)
Maximum landing weight 49,450 kg (109,020 lb)
Max payload weight 13,080 kg (28,840 lb)
Maximum range 5,186 km (2,800 nmi)
Maximum takeoff weight (MTOW)60,781 kg (133,999 lb) 7% E2-190
Maximum landing weight (MLW)52,390 kg (115,500 lb) 6% E2-190
Maximum payload (total) 15,127 kg (33,349 lb) 15.5% E2-190
Maximum range 5,741 km (3,100 nmi)
Keep in mind the CS100 has an 11% higher seating capacity increase over the E2-190 (108 [38-32 pitch] vs. 97 [38-31 pitch] in a standard two class configuration).
While UA would likely introduce a premium economy and might do a couple of other things to get the seating down to 100 seats in a CS100 (like take one of the 3 seat rows out to better fit a second lav in the rear) the introduction of premium economy in the E2-190 would drop the seating down to around 93 seats (which so happens to be a 7% difference).
[Edited 2015-12-19 21:01:26]