Details so far suggest that the x240 will have a 1 soldered in RAM module with a maximum of 8GB. The x230 has 2 sockets so you can currently put in 16GB (maybe more if a 16GB module becomes available in the future). For some things 8 GB vs 16 GB could be quite significant.
Also most reports so far say that the x240 will use low voltage CPUs. So they may be lower clock speed than in the x230.
That's what I heard
, too, and it makes the decision easy. One RAM slot is just out of the question -- it moves the X240 from being a portable workstation to being a sub-standard small laptop. I've been using an X200 for almost four years now and, apart from the aging processor, it's still going strong with 8 GB RAM, an SSD and a new battery. Too bad these small-form-factor powerhouses will be history after the X230.
PS: Just realized that you wrote soldered
RAM...if not even the single slot is user-replaceable, then this is really a laughable attempt at a "business notebook".