so ive been running a Diamond X50A on my roof for about 2 years now and it does fine for hitting the local 2m and 70cm repeaters but theres one about 45 miles out that i can get into maybe 60% of the time and it drives me nuts because i know the path is mostly clear, theres just this ridge line to the southeast that i think is killing me.

been thinking about putting up a small yagi pointed that direction, something like a 5 or 6 element on 2m, just fixed mounted since thats the only direction i care about. but then i lose the omni coverage which i use for local stuff. so now im wondering if i just get a better collinear, like step up to a Diamond X510 or maybe a Comet GP-9 and see if the extra gain helps clear the ridge, or if directional is just the only real answer here when terrain is involved.

anybody been in a similar situation, like trying to work around a terrain obstacle on 2m? is there a point where stacking gain on a vertical is just not going to help and you really need a beam?

yeah terrain is terrain, no collinear is going to fix a ridge line. vertical gain just compresses your radiation pattern toward the horizon but if the path is blocked its blocked, you're not bending RF around a hill with a GP-9. the yagi is the right call here honestly. you could do a fixed 5el M2 or even a homebrew tape measure yagi just to test the path first before you commit to anything permanent. point it at that repeater and see what actually happens, might surprise you how much difference even a modest beam makes vs your omni.

if you really want both options there's nothing stopping you from running a duplexer or a simple coax switch and keeping the X50A up there too, switch to the yagi when you want that specific repeater. bit of extra coax and a $20 switch and you've got both worlds.

i went through basically the exact same thing last year trying to hit a linked system about 50 miles out. ended up just putting up a 7el yagi on a TV rotator which yeah i know is more complicated than a fixed mount but now i can work like 4 different repeater systems depending on where i point it so its actually been really useful. the rotator thing sounds like overkill until you have it and then you wonder why you didnt do it sooner. anyway for your situation if its just the one repeater a fixed yagi is probably fine, dont overthink it