Keep in mind that a graduated cylinder is never meant for accurate volume transfer. You would probably use a Class-A 100 mL buret to transfer 70 mL to a vessel if accuracy were that critical say, 70.0 mL was desired. All these general chemistry rules of thumbs are not useful for real analytical work. Experimental numbers matter the most.
Let us assume you don't have a 100 mL burette. This is how a practical scientist would do it. You would like know whether 7 transfers from a 10 mL cylinder are better or 1 transfer from a 100 mL cylinder is better? You calibrate your cylinders. You know the density of the liquid. You would transfer 10 mL, 7 times and weigh it on an analytical balance. Note the mass and from the mass-density-volume relationship, determine the volume.
Then repeat the same with a 100 mL cylinder, and transfer 70 mL in one go. Measure the mass and hence volume. Whatever delivers the right volume, is the way to go.
Practically, 7 transfers will generate more errors because you do not know the drainage time of the cylinder, i.e., how long should you wait till all the film of liquid is out of the cylinder as the last drop of liquid. Also see the rules for the propagation of error.
By error propagation rules, uncertainties cannot be added like you have shown. It is an incorrect approach. The cylinder with 0.1 mL error will not add up to 0.7 mL by any means. if you make 7 additions.
All the glasswares play a crucial role of serving as the correct measuring equipment in a chemistry laboratory. However, certain parameters differentiate them when it comes to accuracy. While there are many measuring glasswares available such as graduated cylinders, beakers, and flasks; out of all, the volumetric pipette is considered the most accurate one for calculating volumetric analysis. Volumetric pipettes, also known as transfer pipettes, are glasswares that are designed to transfer a specific small volume of the sample solution from one container to another in a very stable and controlled way while maintaining an accurate record of each sample drop. These pipettes are most commonly used in analytical chemistry to analyse chemical reactions, prepare solutions and study scientific properties.
A standard pipette consists of a bulb-like structure in the center, a narrow tip, and a marked unit to determine the level of fluid. It is mainly used as a dispenser in a lab that works based on a vacuum. The air gets sucked followed by the fluid being pulled in and pushed out to the desired container. Volumetric pipettes are specifically calibrated to have the single graduation that delivers and transfers the accurate measurement of fixed volume. Volumetric pipettes use milliliters as the unit of measurement and are available with different fixed volumes. The measurements can range from 1ml, 10 ml, 25 ml up to 50 ml.
Although convenient and less time-consuming to use, graduated cylinders are considered to lack precision due to their large meniscus when compared to pipettes. The long, narrow, and slender neck of the volumetric pipette makes it easier to measure and read the meniscus very precisely. Also, while using other glassware, there is a chance of substance staying on the sides and getting excluded from the measurement, however, the pipette reduces the possibility of that by being responsible for each drop held within.
As opposed to the measuring cylinders, volumetric pipettes also prove beneficial while dealing with potentially harmful substances because of the way they hold the samples. While cylinders have been in use for a long time and are considered the standard benchmark for measuring and transporting the solutions from one container to another, there is a great risk of spillages associated with these traditional glassware methods. While using a pipette there is no chance of the fluid substances flowing over the edges of the glassware and getting wasted. The contents can remain well-placed inside the pipette enabling a quick and hassle-free transfer. This also proves to be helpful even when carrying it around the lab. The units are easily readable eliminating any possibility of human error.
Volumetric pipettes are considered superior to even the graduated pipettes when talking about precision. Graduated pipettes are ideal only for large amounts of solutions where accuracy is not the priority. The volume delivery and precision differ amongst various types, classes, and, built of graduated pipettes, therefore, creating a space for human error to occur.
If high-level accuracy is the concern, then volumetric pipettes are the best choice for reliable results.
Also read: What is the difference between flask & beakers?
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