I would worry less about the overall measurement on factory and more on how they group. Buy 20 rounds of various make cartridges of the type wanted, and shoot them. Pick the ones that shoot best, cycle the best, plus are readily available. No point in buying ammo which you may only get hold of once if you have to re-zero for the next batch.
I'm guessing that you're measuring overall length using a vernier gauge. The differences in length could simply be down to the meplat of each bullet being slightly different which is pretty normal. They can get deformed in manufacture, handling, processing and packaging and it's rare to find bullets with identical meplats, hence why to measure seating depth reliably, you use a comparator gauge.
Whilst price of cartridges may indicate quality of components and costs of manufacture, it is not always an indicator of how ammo will perform in your rifle. However, where bullets are concerned, you tend to get what you pay for. (eg PPU I've found to be very inconsistent in my .308 and at best, just about moa at 100 on a good day but more usually twice that, but they may perform better in another barrel). Deer don't care who makes the cartridge. Hit them in the right place, the guns still goes "bang" and the deer still falls over. Accuracy for your rifle will depend on things like charge weight, seating depth and bullet used. You won't know which combination is best until you try a few. Most factory is loaded to work in a wide variety of rifles and most mid weight cartridges will have a reasonable to long-ish "jump" to work in most magazine fed rifles. I wouldn't over-analyze things at this stage, just shoot, compare and then stick to what you can readily get that works.
For home loading, there's no doubt that if you can make the time for just an evening or two a month, or every two months, you'll make all you need for deer shooting. For regular range work, you'll be dedicating a little more time. I've found loads that so far, no factory ammo has matched for precision/accuracy in my rifles (Sierra Gameking bullets being very accurate...0.5moa). That's not necessarily an advantage for deer shooting at reasonable ranges, but when loading for the range it is, plus that level of precision helps confidence when in the field. Don't discount home loading. Reloading kits can be had inexpensively and if you do some range work as well as deer shooting, it'll pay for itself sooner than you might think.