There are instances where it may be most worthwhile to use the rush buy (no lease) option, but so long as one keeps an eye on income and expenses, the longest lease is a very attractive option, as it can allow you to expand your empire (and hence economy) at near-exponential levels.
It definitely takes some practice to get a feel for it, though, and in any game that you expect to be over 5 years it's probably not worthwhile as more than an opening strategy.
However, for ZYWs it's pretty much the only way to go.
Edit: There are also instances (Starport comes to mind) where the half to dozen week option is cheaper than buying outright. Starport is 156bc outright, but 104+6*7=104+42=146 with the second option, from memory. Granted, not many things are low enough build value for that to work, but there are some.