AWS CLI and difference between its versions issue

I have a program which interacts with AWS Console(EMR/S3) and everything works fine when using the following versions for AWS CLI:

aws-cli/1.3.9 Python/2.6.9 Linux/3.14.20-20.44.amzn1.x86_64

However, due to an existing configuration whatever was successfully ran with the above version, needs to run with an earlier verson of AWS CLI:

aws-cli/1.3.2 Python/2.6.5 Linux/2.6.32-71.el6.x86_64

The error looks like :

aws: error: argument operation: Invalid choice, valid choices are:....

(correct if I am wrong) which basically means that some of the steps that are supported with 1.3.9 are not supported with 1.3.2.

We have many scripts that are running with the old AWS CLi version 1.3.2. The question is on what approach should we take in order to make the above situation work. Shall we just upgrade the version? This however might break things.

An alternative would be to install the new version side by side with the existing one, but I am not entirely confident with this. Anyone had a similar issue or encountered a similar situation?