Which laptop will be best for full developer needs

You didn't give enough information to get useful advice. What types of features, memory (storage and RAM), minimum graphics card required. display size, etc. You didn't even mention what your budget is.

Most PC's become slower over time, indeed, but that's not the hardware but what you put on it that causes it. And because newer software generally has higher requirements than older software.

But I maintain a website written in PERL, and run it for myself as developer (not for the public) in IIS on a 10 year laptop Windows 10 laptop with 4 GB RAM and that's fine. There's not a single reason to replace it.
So it really depends on what you use the laptop for (that is, what you develop) and the reason why it is slow for what you run.

At work, we all have an HP laptop.

Please tell more about your old laptop and the recommended system requirements for what you run.

I will recommend you only three laptops for coding and developing purposes.
I used one of them for apps, games development and multiple other business use. So you can choose one of them according to your requirements

Microsoft Surface Pro 7.
Lenovo Ideapad L340 Gaming Laptop.
Dell XPS 17 9700 Laptops.

Note: irrelevant link removed by moderator.

Here are some options below:
MacBook Pro 16-inch
DELL XPS 15 Laptop
LG GRAM 17
ASUS Vivo book 15 X512

For developers with demanding requirements, several laptops are highly regarded for their performance, versatility, and developer-friendly features. Here are some top choices:

MacBook Pro: The MacBook Pro is a popular choice among developers, especially those working on iOS or macOS development. It offers a powerful hardware configuration, excellent build quality, and a smooth macOS operating system. The MacBook Pro's Retina display, ample RAM, fast storage, and efficient development tools make it a reliable option for developers.

Dell XPS 15: The Dell XPS 15 is a versatile laptop that caters to the needs of developers. With its high-resolution display, powerful processors (up to Intel Core i9), ample RAM, and dedicated graphics options, it can handle resource-intensive development tasks and also a great gaming laptop. The XPS 15's compact design and long battery life make it suitable for both office and on-the-go work.

Lenovo ThinkPad X1 Extreme: The Lenovo ThinkPad X1 Extreme is a professional-grade laptop known for its robust performance and durability. It offers a range of configuration options, including powerful processors (up to Intel Core i9), ample RAM, and dedicated graphics. The ThinkPad X1 Extreme's excellent keyboard, comprehensive port selection, and solid build quality make it an excellent choice for developers.

HP Spectre x360: The HP Spectre x360 is a convertible laptop that combines performance, portability, and versatility. With its 360-degree hinge, it can be used as a laptop or tablet, providing flexibility for developers. It offers powerful Intel Core processors, ample RAM, fast storage options, and a vibrant display. The Spectre x360's sleek design and long battery life make it an attractive option for developers who value portability.

Here are some recommended laptops for developers:
1) Apple MacBook Pro: Powerful, portable, and runs macOS.
2) Dell XPS 15: Sleek design, high-performance specs.
3) Lenovo ThinkPad X1 Carbon: Reliable, durable, and productive.
4) Asus ROG Zephyrus G14: Powerful GPU for gaming and development tasks.
5) HP Spectre x360: Sleek design, solid performance, 2-in-1 convertible.
Consider your specific requirements, budget, and preferences when choosing a laptop.

For full developer needs, a laptop with ample processing power, plenty of RAM, and fast storage is essential. Look for models with an Intel Core i7 or AMD Ryzen 7 processor, at least 16GB of RAM, and a high-speed SSD for quick compilation and data access.