Only you can decide that. Ultraflex cost more than regular LMR, its got a bit more loss and some connectors are not compatible. If you must have good flexibility along the run then maybe you need it. If you can run the coax from your antenna to near your radio with stiffer LMR400, then use a few feet of smaller cable to connect your radio, then maybe not.
Great information! Thanks. I'm looking for the same information. In my scenario, my antennas are located in the attic. Unfortunately I have an HOA. The highest peak of the roof to where my radios are also located in the attic is less then 50 feet. The roof doesn't appear to be an issue, meaning that there isn't any metal under the shingles. It's not the bests scenario, but without a lot of grief it's what I have to deal with. My idea was to use LMR400 to a panel using bulkhead connectors then run the last 3 feet to the scanners. I usually listen to the local stuff in the 154.000 to 159.995 range, I can occasionally hear milair traffic, and the local airports. There are a few trunk systems in the area and the county is migrating to a new radio system that has yet been determined. I have the LMR400 left over from my previous residence, I'd still need to purchase connectors. I thought about using LRM240 but would require both the new cable and connectors, or buy the 50 feet of cable with the connectors preinstalled. My location is in Luzerne County, PA. The antenna I'm using is a scantenna/St2 from the old Grove Enterprises. Since I have the HOA, I'd like to use the best cable setup possible within reason.