Building a 2M setup and debating between a homebrew 8-element collinear versus a commercial 7-element yagi. Collinears claim 3-10 dB gain depending on elements, with 7.5dBd achievable. That's about 6dB better than a 1/4-wave reference and 10dB over a magmount.

However, higher gain means narrower elevation pattern. For local repeater work and some weak signal, which would you choose? Collinears concentrate signal at low radiation angles for better DX but I'm concerned about coverage gaps.

Collinears are omnidirectional high-gain antennas that reduce power radiated skyward. Perfect for repeaters since you don't need to rotate. For weak signal work, the yagi wins hands down - you can point it precisely where you need maximum gain.

I built the SM0VPO design - operational within one hour and gives very nice results. You get about 6dB with 8 half-wave sections, 9dB with 16 sections. The trade-off is worth it for general VHF work where you want gain without constantly rotating.

For contest work, I'd take the yagi every time. Collinear arrays work well for specific applications like 70cm and 2.4 GHz but when you need to work specific directions for multipliers, nothing beats a rotatable beam. Build both if you have the space!