When I started working with Siemens PLCs back in 2017, I thought there was a single 'right' answer for a beginner. I was wrong. I spent about $3,200 overall on hardware and software that wasn't the best fit for my first two projects, simply because I didn't understand the different paths you can take.
In my experience, the choice between a LOGO!, S7-1200, or an older S7-300 for a first project depends entirely on three things: your project's technical requirements, your budget (both upfront and long-term), and what you're trying to learn.
Let's break it down into the three scenarios I see most often in forums and in my own work.
Who this is for: You have a simple, standalone machine or process. Think packaging machine, conveyor control, a simple pump sequence, or replacing a handful of relays. You are not building a factory-wide automation network right now.
This is the cheapest entry point. A LOGO! PLC and the free LOGO! Soft Comfort software can cost under $200. It's incredibly simple. You can program a simple sequence in an hour. Honestly, for a simple relay replacement, it's overkill but very reliable.
In my first year (2017), I used a LOGO! for a project that might need to talk to a SCADA system 'someday'. The client asked for remote monitoring six months later. The LOGO! couldn't do it easily. We had to scrap the controller and upgrade to an S7-1200. The redo cost about $450 in hardware plus a half-day of rewiring. That mistake taught me to look at expansion needs, not just the immediate project spec.
My advice: Use LOGO! if and only if you are 100% sure the application will never need complex communication, HMI integration, or more than 20 I/O points. It's a dead-end for growth.
Who this is for: You are studying to be a controls engineer, you want to build a career with Siemens, or you are working on a project that might grow. This is the path 90% of beginners should take.
The S7-1200 is the current standard starter PLC. It uses the TIA Portal software, which is the same platform used for the larger S7-1500. Learning on an S7-1200 means you understand the core concepts (basic programming, networking) that transfer directly to bigger systems. The market share for Siemens in this mid-range is huge; as of the 2024 market reports, it's the dominant player for this type of distributed control.
From a quality perception point of view, this is where you start looking like a professional. Clients trust a project on an S7-1200 more than a LOGO!. When I switched from recommending LOGO! to the S7-1200 for client projects, my 'project approval' rate improved noticeably—just because the hardware looked and sounded more serious.
I once ordered 10 S7-1200s for a series of small machines. I checked the specs, approved the order, and processed it. We caught the error when the first unit arrived. The problem? I had ordered the standard (non-Safety) version. The machine had a safety requirement for a two-hand control. The whole order had to be returned. The $200 restocking fee plus the 3-day delay wasn't the worst part; the embarrassment with my boss was.
Lesson: Always, always check your safety requirements before buying any Siemens PLC. It's a detail that can kill a project.
Who this is for: Experienced technicians or engineers who already know PLC programming conceptually but are on a shoestring budget. You can find used S7-300s on eBay for a song.
The hardware is cheap. The software is not. The S7-300 uses the older Step 7 software (TIA Portal didn't adopt it natively for years). The real cost is in the time and expertise required. This isn't a beginner's path. The wiring and configuration are more complex. You will need to understand Profibus or Profinet at a deeper level.
I'm not a hardware historian, so I can't speak to the specific legacy compatibility issues. What I can tell you from a practical, 'I-have-to-make-it-work' perspective is that the documentation for a 10-year-old S7-300 is harder to find. The PDF manuals are out there, but finding a specific answer for a fault code takes much longer than for a current S7-1200.
My advice: Only go this route if you are a veteran looking for a budget project for a personal hobby or a very simple, non-critical task. For a career start, this is a dead end. You won't learn the modern tools. The numbers say 'cheap'; my gut says 'steep learning curve.'
Here's the simple decision tree I now use with my trainees:
So glad I figured this out before spending more money. My first big mistake (the LOGO! upgrade) was a $450 lesson. Dodged a bigger bullet when I almost bought a used S7-300 for a client project—that would have been a disaster for support. Take it from someone who has the mistakes on their expense report: for 9 out of 10 beginners, the answer is the S7-1200. Don't overthink it.