As @Cooter says a lot depends on what you plan to do with the brass. If running stiff loads, and I define 'stiff' as matching typical factory load average pressures, say 57/58,000 psi on designs rated as 60-62,000 psi MAP, then you'll pay a lot more for Starline over the life of the case because you won't get nearly as many firings out of it. If your loads are fairly low pressure, both will last as long as you will likely keep the rifle.
Likewise if you never shoot beyond 200/250 yards, you can get away with a lot of inconsistencies in the brass.
I had this dilemma when buying 223 brass. I spent the extra because the starline appears to be very short.
The plan is to shoot them in the 6.5CM, MSRP, 45gr RS62 max, 140gr Sierra SPBT, 2.75” COAL, from a 24” barrel. (I haven’t tried the starline yet as just ordered it, but I’ve been developing with lapua brass so far.
Both the starline and lapua is SRP in this case.45gn is getting close to maximum with thin Hornady brass. If Starline is heavier / lower capacity, it'll likely exceed max pressures. Are the Lapua cases you're using SP or LP? If SP, max loads are somewhere between one and two grains higher to get the same pressure / MV as in LP cases of the same capacity. With Lapua having less capacity than Hornady though this raises pressures and 45gn may be about right for its SP version, possibly on the high side for LP.
Note: never, ever transfer a 'hot' load from SP brass to LP even of the same make without dropping charges and redoing load development.
Sir, sir!Note: never, ever transfer a 'hot' load from SP brass to LP even of the same make without dropping charges and redoing load development.
Sir, sir!
I have had my hand up for the last three or four posts...
SP? LP?
Give the ones good at colouring a clue?
@Stalker1962 SP ignition is considerably weaker in this size of cartridge than LP, especially if the case has the smaller diameter flash-hole. So you generally, but not invariably find that when talking 40-45gn charges of most extruded powders, the SP version with its weaker ignition needs, 1, 1.5gn additional powder to achieve the same MVs as that powder in equivalent LP brass. As MVs are directly related to pressure x time, the SP's lower velocity suggests lower pressures.
Conversely, if let's say you've worked up a max and 'hot' load to 46gn in SP brass, simply transferring that to an otherwise identical LP case, will most likely see you OTT pressure-wise by 1-1.5gn, and now you're firing it in a weaker case as the LP case-head doesn't accept as high pressures in any given case-head diameter.
One reason why many match shooters adopt small primer brass where available is to be able to run at max SAAMI / CIP pressures and retain decent case life because of the stronger case-head and web. Peterson and Lapua 6.5 Creedmoor will take repeated firings at the cartridge's 4,350 bar / 63,091 psi rated peak pressure, but you'll only use the case once at that pressure when it's made by Hornady.