Introduction:
When deciding whether to focus more on mathematical physics or electromagnetic theory for Paper I, it is important to consider the syllabus, your strengths and weaknesses, and the weightage of each topic in the exam. Both mathematical physics and electromagnetic theory are essential subjects in the field of physics, but understanding the specific requirements of the exam will help you make an informed decision.

The Syllabus:
1. Mathematical Physics:
- Mathematical methods of physics
- Classical mechanics
- Quantum mechanics
- Thermodynamics and statistical physics
- Electronics and experimental methods

2. Electromagnetic Theory:
- Electrostatics and magnetostatics
- Electromagnetic waves
- Optics
- Electromagnetic radiation and interaction with matter
- Quantum theory of light

Weightage and Difficulty:
1. Mathematical Physics:
- Mathematical methods of physics: This topic is crucial for solving problems in all areas of physics. It requires a strong understanding of concepts like linear algebra, calculus, and differential equations.
- Classical mechanics: This topic is usually considered challenging due to its mathematical complexity. It involves the study of motion, forces, and energy in systems ranging from particles to celestial bodies.
- Quantum mechanics: Quantum mechanics is a fundamental theory in physics and is considered difficult due to its abstract nature. It deals with the behavior of particles at the atomic and subatomic level.
- Thermodynamics and statistical physics: These topics involve the study of heat, energy, and the statistical behavior of large systems. They are relatively easier compared to quantum mechanics.
- Electronics and experimental methods: These topics focus on practical applications and experimental techniques. They require a good understanding of circuits, measurement techniques, and data analysis.

2. Electromagnetic Theory:
- Electrostatics and magnetostatics: These topics deal with the behavior of electric and magnetic fields in static conditions. They require a solid understanding of vector calculus and Gauss's and Ampere's laws.
- Electromagnetic waves: This topic covers the propagation of electromagnetic waves and their properties. It involves concepts like wave equations, polarization, and interference.
- Optics: Optics deals with the behavior of light and its interaction with matter. It includes topics like reflection, refraction, lenses, and diffraction.
- Electromagnetic radiation and interaction with matter: This topic focuses on the interaction of electromagnetic waves with various materials. It includes topics like absorption, scattering, and emission of radiation.
- Quantum theory of light: This topic relates to the quantum nature of light and its particle-like behavior. It involves concepts like photons, photoelectric effect, and quantum optics.

Conclusion:
In conclusion, both mathematical physics and electromagnetic theory are important subjects for Paper I. The choice of focus should depend on your strengths, weaknesses, and the weightage of each topic in the exam. If you have a strong mathematical background and are comfortable with abstract concepts, mathematical physics might be a suitable choice. On the other hand, if you have a good understanding of vector calculus and are interested in the behavior of electromagnetic fields and waves, electromagnetic theory might be a better option. It is important to allocate time and effort based on the syllabus and your own abilities to ensure comprehensive preparation for the exam.