a few things here....
1.) Welcome
2.) Make an intro thread if you haven't already with some pics of you and your bike
3.) Have you inspected the chain, and found 1 or 2 bad links?
4.) Have you properly adjusted it?
Sometimes you can "resurrect" a chain by cleaning it thoroughly with WD40 or simple green, adjusting it properly, riding it till it's hot and then shooting some new chain lube. If you have a bum link though, you will have to replace it....
so...
5.) when replacing a chain you SHOULD also replace the sprockets. They wear together and replacing just the chain OR the sprockets causes the replaced part to wear excessively fast.....
6.) To answer your original question - I've used a master link through 3 chain replacements.... If you want to buy the crimping tool for the solid link, go for it, but it's a bit of a pain... a 520 is overkill for a 250 anyway, so the master links tend to hold up very well.