I have just been doing the same thing in my company.
I checked with tech support on the twido, and they tell me you can not Remotely link up to these PLC's. This is no good for me as I will be linking about 15 of these together, and eventual I want to be able to accese them over a modem conection. In a few months they will be coming out with am eathernet Twedo, which should solve that problem. I also find that the programming software on the twido is horable (In my opinion). The Twido can comunicate with any thing that uses modbus, so you can use HMI's, Pacific Seintific stepper drives, Emerson Servo Drives, ect.
The Micrologix 1500, has way more functionality and I like the software (but then again I am used to working in RSlogix 500). With the Micrologix I can go to modbus. devicenet, eathernet, DH+, and other AB protocols. The cost is about the same as far as I can see, with the exeption of the software (AB likes to rape you there). What I am not sure with the 1500 is if you are limited in some the programming, ie can you do trig functions, PID loops and the other more advanced functions.