Curious to see what people prefer in regards to WL.
I'm not sure that this is a like for like comparison. The WLIP obviously has the key extra features of having an Ethernet interface and being able to upload to the weatherlink.com website, but costs substantially more. If you don't need these extra features then I'm not sure why you would pay the significant extra cost over eg the standard USB logger.
But if you like the idea of having live weather data on a website (at least in a basic style presentation) with a total minimum of set-up hassle and don't want to run a PC locally 24/7 then you might feel that the extra cost is justified (quite a few schools fall into this category).
Based on our own sales figures, I'd say that the USB logger (+ 6510SER) currently outsells the WLIP by a ratio of 3 or 4 to 1.
EDIT: And the poll should say WL hardware not software - the software is identical between both types and does exactly the same things.