See my thread “Backup to My Tablo” for some considerations about having both:
The Homeworx (and clones such as iView) is great for recording sports events in native (OTA) mpeg2 format which is better than Tablo’s MP4 for picture quality. Plus it’s usable for projectors as a tuner with time shifting. Personally I prefer having Tablo + Homeworx over upgrading my Tablo from 2 to 4 tuner. At $30 it’s not much of a cost. I feel safe having an inexpensive backup should anything happen to my Tablo.