I had a better experience with sazz than spalt, sazz went so well in an amber ale I did that I posted the recipe. I oaked that beer so I could have been infatuated by the oak character and its smoothness also. From my notes I did a spaltz select Amber ale which I didn't note the taste of it but did recognize it as englishy using 04 yeast. I used 05 in the saaz amber also making it a bit different.And gravitys were far from each other 1.06 for saaz and 1.043 for the spalts. That said I would have to brew them again to remember how I would compare them, they are both mild and used commonly in lagers. And go well in the right beer and esb could be a good choice I believe maybe not commonly per style though and could be interesting. I like Goldings even more though. As far as just bittering, Sazz is smooth to me, and mildly hoppy not shure about spalt I think it may have a bit milder sharper edge mild but sharp citrus maybe to it possibly or little more spice/pepper noted from memory.
You can also look up descriptions of hops to like on websites, etc. Although I commonly don't agree with them 100% as it varies but you can get a general idea but there is nothing like going with your own experience and that's the fun of brewing. Its not fun getting old hops though or poorly stored hops.
Heres the ones I used descriptions:
Saaz:
Fresh from the master growers in New Zealand, this new hybrid of Saaz is a welcome addition to the world's selection of organic hops. Saaz is renouned for a mild earthy spiciness and clean aroma, and is widely used in European lagers, especially the Pilsner style. The New Zealand Saaz is bred from Saaz rootstock hybridized with organic New Zealand stock. Although a newcomer on the hop scene, this hop is already in use by several prominent breweries.
German Spalt Select Pellets
6% Ave. Alpha. Exceptionally fresh and aromatic, the Spalt Select are one of the best organic hops we have found. Bred from Mittlefrueh and Spalt hops in the early 90's the aroma of Select hops is reminiscent of a fine Tettnanger or Hersbrucker noble hop. A hop suitable for bittering, flavor, and aroma, it is excellent in European ales and lagers, with a pleasant spicy flavor and strong aroma. A good substitute for Tettnanger, US Saaz, Hersbrucker
I also would like to add in my experience I have really liked almost or all NZ hops I have ever used before.