PSPs are great and i advise you get one!
1.50 can play homebrew but so can any Custum Firmware - 2.71 SE - and any OE Firmware
The chances of bricking from CF is very slim, downgrading has more risk but yet if you do it right you wont have any problems!
3.40 OE has all the possibilitys of 1.5 plus many more!
Best Emu - N64
You can still play all the official games with 3.40 OE, with 1.5 you need Devhook
Not much apart from experiencing it yourself and then deciding on how good it is!
You wont regret doing this is you get it all right