I can suggest based on having owned and used both. I started with the portable when I owned my ERA class B motorhome. I now own a 33' Wildcat Maxx TT and had the dealer install/hardwire my Progressive 50 AMP unit in my TT. I much prefer the hardwired unit for the following reasons:
1) the portable unit is plugged into the post so it's relative unsecured.
2) You have no idea of what's going on with your power after you initially plugin into your unit since the readout is external to your unit.
3.) I felt it was just 1 more thing to do when setting up camp and if the Progressive unit shut off the power due to a lightning strike, etc, I had to go outside to reset it.
No question in my mind, the extra cost of the hardwired unit was $$ well spent!
Days camping (2015)----88 days
Days camping (2016) ---110 days
2016 Wildcat MAXX 28RKX (33' TT), 2007 13' Scamp
2015 Ram Laramie Hemi
30 years RV'ing
12 different RV's