I've got the ecab and eroll and find the combo works great or me. It's good to buy a load of atomisers that work for both and I really like the tank/atomiser system. I have tried the evod the t3 and vision nano, none of which I am, personally, very keen on. So, if you like the eroll, I'm sure you will most likely be happy with the ecab, very similar system, just larger tanks and batteries. I use the ecab at home or driving and the eroll in more social situations, and have found no need yet to upgrade to anything more.
Compared to when I started out in 2008 (and gave up!) , tea bag fillings, continual dry hits etc, these two ecigs have got me off the cigs and I am very thankful at how simple they are compared to the "old days".