Adobe illustrator is the standard among professional grade design softwares for PC. Ive been in the field of designing for quite some time now and been using illustrator for the beginning.
Its one for the best softwares available for designing purpose. Adobe Illustrator has a wide variety of tools and features available it for achieving any difficult looking designs with ease.
Adobe Illustrator is much suited for creating new designs from scratch. That doesnt mean its not able to edit currently present design. That can also be done with great accuracy.
All the created can be exported in different formats including svg, which is scalable vector graphics. This format helps in increasing and decreasing the images or design size without damaging the file in any way. That means it will remain in the good quality even if stretched out.
Totally, Adobe illustrator is one of the best designing software available in the market. The only concern is the price of the software. If its affordable to you, then you wont regret your decision.