Proxies Vs. Adapters: When to use Proxy?

Could somebody list out the scenarios where you would Proxy and where you would use Adapter?

Use Proxy or Adapter: What is the best practice to develop my integration?

An Example Scenario:

Let's say I have data from legacy systems in legacy format in text files. I have a standard to BAPI to call to send to R/3. But, I need to do some lookups, code conversions etc. before I call the standard BAPI. So, we write a wrapper ABAP fucntion, inside there we write lookup codes, and then call standard BAPI.

Should I do this scenario using Proxy or regular RFC adapter?

Thanks.