If you practice tilting a 1 x 120 (2 x35mm) tank can be filled in 4-5sec. Which is the same as paterson tank (I have measured). But Patterson tanks do drain much faster. A 2 x 120 tank takes me 8sec to fill.
Also check the amount of developer you need to use. The smaller the amount you need to pour in, the faster it will be.
15 seconds is negligible compared to 10 minutes but it's significant compared to three minutes. So if you're worried about filling time affecting your film, you could choose a developing method that requires more developing time.
Tilt the tank of course, but if you have a really large tank, it makes sense to fill in the dark and lower the reels in on a rod. If you have a tank with an old stainless lid, you might get a new plastic Kindermann lid. Those fill faster.