Best approach for version compatibitliy testing

Hi- I would like to know any suggestions/comments about the best way to perform version compatibility testing for the below scenario.

I want to pass in the same input for different versions of the same webservice, to make sure if doesn't break any old functionality or returning a wrong value. Expected value is captured using Run 1.

Run 1 : Web service version 1

Step 1: Get input values from datasource
Step 2: Send a request and validate the response
Step 3: Groovy script. Count number of nodes return. Insert the response values for each node to a sql database. Each response produces "n" number of rows and "k" columns
Step 4: DataLoop - has "m" rows

At the end of the run1, my sql table has "n X m" rows containing "k" columns each.

Run 2: web service version 2

I would like to use the same input values from the datasource and perform Step 1 and Step2.

Now my question is
1) Do I create a subreport instead of step 2 and compare the response against the db values captured from run1?
2) Do I write it to another sql table and then create another step to validate one table against another?

If choice 1, I would have to compare "k" columns for "n X m" number of rows. Is it possible to perform that using groovy script?
I have no idea how to deal with solution 2.

Appreciate if someone had dealt with the same kind of scenario before and would like to give me some suggestion.

Thanks!
Sanjeev