Last time I went, both. Haven't been for a few years but I used to take a bag of old collectible stuff and trade it in for oodles of LPs with tatty sleeves but good condition vinyl. Don't take a lot of money as you may well spend it.
It depends on what you are looking for. The teenage convert used to make a fair mint from specialising in metal records, mainly from this fare and selling them on ebay. I remember picking up Hellhammer - Apocalyptic Raids for a fiver & selling it on for £40, similar story with Celtic Frost - Morbid Tales & Death - Leprosy.
I go a few times during the year - it's certainly scaled down from the manic two floors of the Brighton Centre it used to be! There are bargains to be had, but you obviously need to have a good dig to unearth them. You can't really go there with a 'want list' in mind either because you'll hardly ever find them, but you'll always go away with bargains that you might not have expected to get if you go with an open mind.
There also the dealers there with the 'trophy' records on display behind their stall with mad prices on, more for showing off than actually willing to sell them...........guarantee that these will be on display the next time too! The warning from an earlier poster is good too - you will spend whatever amount you take