Hi Sarah Mayer,
I would use smart lists as they would be easier to manage and make amendments to, which I think you will want to do as you refine these lists going forward.
I would only use segmentations when you have multiple definitive groups to slot leads into under each category, examples would be:
Region: EMEA, APAC, NA
Industry: Financial, Medical, Educational
Product Range: Range 1, Range 2, Range 3
The reason you would use segmentation is so that you could personalise the emails and messaging you are sending to them with snippets, i.e. replace the footers with regional based footers that have different office addresses, telephone numbers; swap email banners based on industry etc...
From your description above I would say you are wanting to create siimple batches of people using filters, that are not overly related or that would be broken up further. If that is the case I would use Smart Lists and create them in the database area.
Others may have different opinions though, thats just my 2 cents
Thanks Gerard! I agree. Fingers crossed it goes well