As a general rule, anything working with strings is going to be slower than working with numbers. Concatenation, in my experience, is likely to be particularly slow. Therefore, using Substring is really important in this case. However, it looks like your data is going to contain a certain amount of text info, which means that you will be using strings, like it or not.

Be sure you have Option Strict ON, as that generally increases efficiency. I have a feeling that the efficiency increase with Option Strict is greater for strings, but I suspect that is not really true.