A discone has 0dB gain, so by the time you add in feed line loss, you are going to need a fairly strong signal to make everything work.
Using a band specific antenna with gain and good coax will easily outperform a discone when working with weaker signals. It isn't hard to get a UHF antenna with gain, it can still be physically short and work well.
I've used a few Laird base antennas with good results. Properly installed it should last quite a long time.
OK, I've used similar antennas on 800MHz.
Pretty good antennas for the price,
The FG4500 is zero gain, so you'd be getting roughly the same performance as the discone.
The FG4503 is 3dB gain, so it would get more signal down the coax to your radio.
If you can, you might want a higher gain antenna.
I'd also look at the FG4505 and the FG4507. Unless you have space/heigh constraints the prices are a bit higher, but not much. The higher gain will give you better reception, stronger signal to your radio, and might allow you to hear traffic you might not hear with the lower gain antennas. Usually higher gain antennas have a different radiation pattern on the transmit side, and this is something to consider if you were transmitting with it. But for a receive only application, the higher gain might be a benefit.