I have used many..many different aftermarket batteries for my LG devices over the years and never had a problem. I always purchase a brand that has a positive review history on Amazon for the basic protections of not blowing up or melting down and I have been good.
There are some basics that you should expect...
1) Battery life varies between not only the manufacturers but within the same brand & batch. Not by much but it seems that each battery acts a bit different.
2) The batteries last for years but with constant usage the chargers will burn out about every 8 months or so due to heat and the fact that there is not ventilation in those little plastic boxes. I have been able to prolong their lives by drilling a couple holes in the charger bodies to get a bit of air movement. but they are cheap to replace so no big deal buying a new one every 8 months or so.
3) On Amazon the battery capacity ( mAh. ) are fairly accurate but on Ebay you are dealing with more of a sketchy group of vendors typically from china and they don't mind adding a few ( mAh's ) to there description to help customers make there decision but if the batteries have the same dimensions they typically have the same capacity. So if you see a replacement that says " High capacity replacement 4200 mAh " and the OEM is the same size and is " 3200 mAh " then count on it being around" 3200 mAh ".
Had good luck with these brands : ( TOTHL, JUBOTY, Trendon, Sporting persistance )