I have never used a Maldol MH-209 antenna but I have used a Diamond SRHF10. It is about 2.75" tall and it is a terrible antenna that works perfectly when I need a stubby. It works best on UHF, but I have reached a repeater 4000' ASL and 35 miles away on VHF with 1.5 watts using that Diamond antenna. Please note I was outdoors and the radio was a Yaesu VX-3R.
Holy cats! For fun I just tested that Diamond antenna and Yaesu radio again while I am indoors to a different repeater that is about 25 miles away at a 4000' elevation and it worked. This time I was on UHF. It did not work on VHF into the same repeater location. While my signal/audio into these repeaters may not be the best coming out, it was understandable.
While longer, yet thin, I have a Nagoya NA-666 that works a little better than the Diamond SRHF10.
My best HT antenna for 70cm is a Diamond RH951S. It beats out my Diamond 320A and RH-77CA antennas, but they are all much longer than that stubby.
P.S. I also use several Diamond SRH-805 antennas, but on 15mw fox hunting transmitters where a poor performing antenna is what I want.