Personal experience only here...
My first PWS of any kind was (is) a Davis Vue with a USB logger. It seems that this setup is the tipping point for most. The techies and hackers like to move to something higher up (Pro2) while the backyard enthusiasts may not want to spend quite as much as you do for the Vue. The software for Davis is essentially the same (except perhaps for the "IP" version) and it was not too difficult to set up for Wunderground. It also was quite easy to get my own website set up and then to later join CWOP. The Davis (Vue) can be quite a distance from the console without difficulty, but USB limits your distance between console and PC (or router with "IP" version) unless you get creative or opt for the "serial" version.
My latest PWS is a LaCrosse 2813 completely wireless system. I got it at Costco for $80 as a gift for my father-in-law who enjoys checking MY weather station online, but would never imagine setting one up himself (150 miles away). The setup was a snap, and with the addition of WUHU software it was even easier to get on Wunderground than the Davis. Drawback is the performance of the wireless system. Short distance, line-of-sight only from wind and rain gauges to temp-station, from temp to console and from console to USB transceiver.
No personal experience, but there are threads on this forum about the newest Acu-Rite that has a provision to upload to WU, but seems otherwise limited options beyond it's own mybackyardweather application at this time. It seems like it would be easy to set up however, and is priced somewhere between the LaCrosse and Davis units I mentioned.
In addition to the points above, you may consider how much further you want to take your online weather experience than Wunderground, such as CWOP or your own website. There are many versatile software packages out there that perform better on certain PWS ystems/platforms than others.
Whatever you decide, please return to this forum to share your choice and how you came to it. It will help the next person with the same question.