The best oral only cycle is not doing one.
But seriously, if you are hell bent on doing one you could hypothetically do either. I know a few friends that feel fine or better than fine on dbol only, but they certainly don't "gain some lean muscles". They gain a lot from a 4-6 week cycle, like 10-15 pounds, but they keep almost none of it maybe 2lbs if lucky, the longest cycle i've seen was 12 weeks and that guy ended up keeping 5 or 6lbs, which given the damage to his liver (his enzymes were about 4x the high end after 3 weeks of pct) and lipids it's not worth it, and also given his level of development, he probably could have gained 75-80% of that by eating more and being more dedicated to training. Although I have to say the dude did look swole as fuck for 12 weeks.... but pretty normal after.
Anavar only isn't that much better in terms lasting lean mass, you will gain even less. Although you may benefit from some fat loss if that is what you are after. Overall if you want gains that last oral only is pretty stupid, you'll end up temporarily fucking up your liver and your libido (for some that's a little more permanent). If you really want to do it, use dbol if you want to give the appearance of being huge for x number of weeks and use anavar if you want potentially lasting fat loss if you keep your diet up afterwards. But really if you value lasting gains and being able to get pussy on cycle, man up and pin