OP270 or OP27 instead of OP25/A

hi people,
I have got s5-115u (cpu943b)that communicated OP25/A.
I want to change this OP25/A with new one.Therefore I could not decide whether OP27 must be use or OP270.IF I use OP270,Can I meet what kind of problem?Is the additional software for communication needed for this?For example standard FB's..
thanks for your efforts....

I dont know if it is necessary with standard FBs or not, but I suspect that OP27 and OP270 work the same as OP25 connected to an S5 via the PG port.

A small snag:
The OP27 has the same TTY port for the connection to the S5 PLC.
The OP270 only has a RS232 port. So it needs an aditional adapter to connect to an S5 PLC.

The OP25 program will convert easily to OP27.
When converting from OP25 to OP270 there will be a number of things that cannot be converted. This must be checked manually.

On the other hand, the OP27 is allready obsolete.
The OP270 is the current model (there is allready an OP277 under way though).

Thanks .I decided to use OP270 despite to difficulty.Now single thing for rest whether standard FB's is needed or not.?...