How to correctly prepare a standard solution?
The reason you are using a weighing glass is because it is a lot smaller and it has a much smaller mass than a volumetric flask. These glasses usually are more stable, less affected by temperature, and pressure changes, or drafts in the laboratory. The smaller surface also tends to not accumulate much dirt due to static, your hands, etc.

If you were using method one, then you could skip the part with the weighing glass altogether. This method suffers from getting a stable reading as due to the size it is more affected by the conditions in the laboratory.
Method two is certainly the better method, because the total error tends to be much smaller. When you are using such equipment, then your concentrations are typically smaller than 1 mol/L and you are working with small quantities of solid substances. Continuously rinsing out the weighing vessel will ensure to transfer almost all of your solute.
If you were to produce a saturated solution, then the mass of the solute would not matter in the first place. 

If your compound does not readily dissolve then the attempted concentration is too high to be used for analytical chemistry and you should rather start from a saturated solution. All primary standards are easily dissolved. If you are not dissolving a primary standard, then your should check the concentration against one.

Therefore, method one can be used if accuracy is of a minor concern (leave out the weighing glass) because it has to be determined again with a primary standard. Method two should be used when preparing accurately concentrated solutions of primary standards.