I guess it depends when you're going to hunt. If you're bow/ML I run with multiple cow calls and bugle tube. I need my hands to be motionless with a nocked arrow at times so I favor diaphragm calls at the crux moment bow hunting. The mellow momma diaphragm is pretty forgiving for cow calling but I prefer other diaphragm calls if I'm mixing bugles in the mix with my cow calls. You can do a lot of tone changes and different calls with a diaphragm but it becomes more difficult when I'm stressed and in so tight I can't afford to screw up. That tension that wells up in my neck seems to effect my tongue sometimes.
If I'm unlucky enough not to have an archery tag and I'm stuck rifle hunting I never bring a bugle tube. Although I've heard plenty of bugles after 4th rifle, I've only heard a few locator bugles during 4th rifle. I generally will bring a diaphragm that I can cow call with or bugle. If I need a tube I'll roll up my map, but truth be told I just don't need to call during rifle season and most the elk aren't talking. Funny how they know hunting season is over.
Now there are a couple reed calls I really like for their nasal tone, but I need to use my hands with them so that's a consideration. One is a wood body cow call I've had since the 90s. It says "Woodwise, Franklin TN" on the call. The other is the Primos Hyper Lip.
Now for full disclosure. I'm not out there calling much at all. Even during archery season I prefer to slip into the mix and let the real elk do the calling then have elk hunting me as the lone caller. I have experienced first hand leaving a set only to find elk **** 30 meters away where I was obviously being watched and probably laughed at. I also don't like calling in hunters.