It really comes down to how bad you want a power meter for outdoor use. PM + a wheel on trainer works fine and if you are on a budget and what power all the time is the way to go. A wheel off smart trainer is better, gives you access to erg mode and sim mode (i.e. Zwift). A smart trainer gives you in essence an indoor power meter which is a significant step up from virtual power.
For me, virtual power on my old fluid trainer to a pm on the bike + my same old trainer was a HUGE improvement. that improved indoor training but more importantly revolutionized out door training and riding. 2 years later I got a Kickr Core and I love it and would not go back but it was not as big a leap as just getting a PM and using it on 100% of my rides indoors and out.