If you have very rocky soil or a lot of trees or high bedrock and such, I'd go with the flexible line. If you have soft or sandy soil and deep bedrock, you can go with sections.
To me, the best way is NOT the cheapest. For a 2800 ft. run, I'd get as MUCH contiguous pipe as I can! (That means use a roll of pipe.) Be sure to 'mark' your soil where you have connections. In case there are leaks, I hear that it's good to know where the connections are. Be 'aware' of what you're driving and/or potentially-building where you run your line. If in the future, for example, you want to build a garage, you don't want to have to move the line!
My best to ya and hope this helps.
PS: After this afternoon, I won't be back until Monday morning. 'Other Follow-uppers' (including Steve Jones), will be around ...