Hello there! Based on your needs, I would recommend using Gradescope. This tool allows teachers to grade both individual student assignments and exams, and it provides detailed analytics on student performance. This feature could be particularly useful for comparing written report cards and identifying any significant changes in student grades compared to previous results.

The AI-Assisted Grading feature of Gradescope can help grade written exams and homework, which could be beneficial if you're dealing with a large number of report cards. Additionally, the Dynamic Point Adjustment Rubric allows for on-the-fly changes to rubric items and values during grading, which could be useful if you need to adjust your grading criteria based on the changes you observe in student grades.

Moreover, Gradescope integrates well with learning systems like Canvas and Brightspace, making it simple to add class rosters and push grades to these systems. This could be a time-saving feature if you're already using these platforms.

Please note that while Gradescope is a powerful tool for grading and analyzing student performance, it might not directly compare report cards. However, the detailed analytics it provides can certainly aid in identifying significant changes in student grades.