I normally throw 15lb equipment, but I got stuck getting a 14lb spare ball because it was all the pro shop had in stock when I needed one for my PBA Experience league (good luck shooting spares with an aggressive ball on those oil patterns!!!!). It DOES make a big difference. I have had to get used to the different armswings and releases I need. However, luckily after a full season, I'm pretty much used to the spare ball now and only miss spares when I just have a total brainfart. I however do NOT recommend going between weights on purpose for your spare ball! It just makes things more difficult.