they are two totally different breeds first of all, oegbs are decendants of fighting chickens, so they have temperment issues, you will have to dub your birds combs and wattles for show. they are more common so you will have an easy time finding a REPUTABLE BREEDER TO BUY FROM. if you are looking to show, you will have to buy from a breeder as hatcheries sell poor excuses of breeds. oegbs are cheaper than seram. the oegbs are different than seramas, they are an accepted aba breed, have a completely different stance and standard, and come in different color varieties than serama. i like serama better, because they are more unpredictable, and unpredictability is what keeps things interesting and fun. Seramas are known for their vertical stance, and somewhat extreme pose, with their huge chests and straight tails, they stand more vetical. it depends on your preference, the extreme type and docile nature of a relatively bird native to Asia, or a classic elegant breed that has been bred for a long time in england
as i always preech, before you get a breed, join the breed club of that particular breed, this will open a gateway to knowledge and get you a front row ticket to the best connections and breeders, STUDY the standard drawings and descriptions, and then choose good birds from a good breeder.