I think the biggest general issue is the cost and availability of oral primo tabs. Back in the day they were available but they've probably only surfaced as more available in the last couple years. I guess w/ the myriad underground labs. Those also come w/ the usual caveat of "are they really what they claim to be" because you're frequently not talking about pharma-grade quality assurance & dosing. Because primo tabs haven't been readily available for many years I couldn't speak to any history of faking or not. Primo depot has a big history of being very expensive and frequently faked.
What are primo tabs good for? Primobolan (depot - injectable & acetate - oral) is generally known as a great cutter - it doesn't aromatize and does a reasonable job of maintaining muscle during a competition cut. As most AAS, also introduces a great recovery capability during the stress of competition prep. Primo is notorious for hairloss.
Looking at tabs specifically, there's a high anabolic to androgenic ratio which is normally great, but the overall gain from the compound is kinda small. Also given that you lose alot w/ the compound passing thru the liver. The caveat that comes w/ this is that if you're expecting this compound to support you thru an aggressive competition cut, you may actually find yourself over-extended and not getting the muscle support (i.e. not a large overall anabolic presence).
In the actual use of primo tabs - anecdotally from some old school female BBs, the use of primo tabs in contest prep is to crush them up & use them topically w/ DMSO cream. This is because so much of the power the compound is lost in its first pass through the liver.
So to compare to anavar - it matters first what you're trying to do or what you expect. Anavar is always the preference for someone newbie to AAS. It is more predictable, more mild, good gains, occasionally a bit of water retention, but a decent balance of anabolic, androgenic, no aggressive sides at low doses, and can be run at a long duration w/ minimal issue, all for good results. Primo tabs are going to be mild but limited in their 'gains' ability because it is overall low anabolic effect. People may like the lack of water retention - which makes this really focused on a cutter and not a bulker, but as a dry cutter - will also bring sides like hair loss.
So recommendation - if you're looking for a starter AAS - would always go w/ anavar. If you're looking to use it during a prep, would probably stack it w/ something else that has a higher anabolic contribution to help preserve muscle mass during the cut. The primo tabs would contribute to the "cutter" aspect, but need help in muscle preservation. And if you're at the point where you're stacking, you should also be at the point of being accepting and responsible for the more aggressive sides of bigger compounds and stacking in general. And for the cost of primo tabs (unless you got a sweet hook up), there are probably a number of other options if you're seriously considering stacking & use of stuff more aggressive than anavar. If you've got the good hook up and can handle the expected hairloss (Note - if you're using any dry cutter -primo tabs, primo depot, winstrol, etc. - get a bottle of Nizoral shampoo to help reduce DHT-drive hairloss) then a stack of var + primo tabs might be a good combo.