When it comes to military-style dive watches, Seiko MilSub watches (Military Submariner) are a top choice among enthusiasts. Known for their durability, rugged aesthetics, and reliable performance, these watches are available in automatic and quartz variations. But which one is the better choice for you?

In this guide, we’ll compare automatic vs. quartz Seiko MilSub watches, discussing their pros, cons, and how they fit different lifestyles. Whether you're a collector, an adventurer, or a daily wearer, this comparison will help you make an informed decision.

What Is a Seiko MilSub?

A Seiko MilSub is a Seiko dive watch inspired by military-issued timepieces, particularly those used by naval forces. While Rolex produced the original MilSub for the British Royal Navy in the 1970s, Seiko created affordable yet robust alternatives, including models like the Seiko SKX series, Seiko 7C43, and Seiko SNJ025.

Seiko MilSub watches often feature:

• High water resistance (typically 200m+)

• Durable case construction (stainless steel or titanium)

• Legible dials with strong lume

• Rotating bezels for dive timing

• Military-inspired designs (black dials, sword hands, matte finishes)

The choice between automatic and quartz movement affects the performance and usability of these watches. Let’s break down the key differences.

What Is an Automatic Seiko MilSub?

An automatic Seiko MilSub is powered by a mechanical movement that winds itself using the motion of your wrist. These watches do not require a battery but need regular wear or manual winding to stay running.

Pros of Automatic Seiko MilSubs

✅ Mechanical Craftsmanship – The intricate design and self-winding mechanism make automatic watches highly desirable among collectors. ✅ No Battery Required – Unlike quartz watches, automatics don’t rely on a battery, making them more environmentally friendly. ✅ Smooth Sweeping Seconds Hand – Instead of ticking every second, the hand moves in a smooth, continuous motion, which many enthusiasts prefer. ✅ Long-Term Investment – Well-maintained automatic Seiko MilSubs, such as those with the Seiko NH35 or 6R15 movements, can last a lifetime.

Cons of Automatic Seiko MilSubs

❌ Requires Regular Wearing – If not worn for a couple of days, the watch will stop and need to be manually wound. ❌ Less Accurate than Quartz – Automatic watches typically gain or lose 5-20 seconds per day, whereas quartz movements are more precise. ❌ Higher Maintenance Costs – Automatics need servicing every 3-5 years to ensure optimal performance. ❌ More Expensive – Automatic Seiko MilSub watches generally cost more due to their complex mechanics.

Popular Automatic Seiko MilSub Models

• Seiko SKX007 – A classic, military-style dive watch with the reliable 7S26 automatic movement.

• Seiko SRP777 ‘Turtle’ – A vintage-inspired MilSub with a cushion case and a 4R36 automatic movement.

• Seiko SPB143 – A premium automatic MilSub with a 6R35 movement and 70-hour power reserve.

What Is a Quartz Seiko MilSub?

A quartz Seiko MilSub is powered by a battery-operated movement, using a quartz crystal to regulate time. Quartz movements are known for their high accuracy and low maintenance.

Pros of Quartz Seiko MilSubs

✅ Extreme Accuracy – Quartz watches typically lose or gain only a few seconds per month, making them more precise than automatics. ✅ Low Maintenance – Requires a battery change every 2-3 years, but no need for regular servicing like automatics. ✅ Durability – Fewer moving parts mean less wear and tear, making quartz Seiko MilSubs ideal for rough conditions. ✅ More Affordable – Quartz models are generally cheaper than automatic counterparts.

Cons of Quartz Seiko MilSubs

❌ Lacks Mechanical Appeal – Watch enthusiasts often prefer the craftsmanship of an automatic movement. ❌ Ticking Seconds Hand – Unlike the smooth sweep of an automatic, the seconds hand on a quartz watch moves in distinct ticks. ❌ Battery Dependency – Eventually, the battery will need to be replaced, which can be inconvenient.

Popular Quartz Seiko MilSub Models

• Seiko SNJ025 ‘Arnie’ – A hybrid quartz-digital dive watch with military roots and solar charging.

• Seiko 7C43-7010 – A vintage military Seiko quartz diver known for its toughness and reliability.

• Seiko Prospex S23629J1 ‘Tuna’ – A professional-grade MilSub with a high-accuracy quartz movement.

Automatic vs. Quartz Seiko MilSubs: Which One Should You Choose?

Choose an Automatic Seiko MilSub If:

✔️ You appreciate mechanical craftsmanship and traditional watchmaking. ✔️ You don’t mind winding your watch or wearing it daily to keep it running. ✔️ You prefer the smooth sweeping motion of the seconds hand. ✔️ You are looking for a long-term investment and willing to maintain it.

Choose a Quartz Seiko MilSub If:

✔️ You need extreme accuracy without adjusting the time frequently. ✔️ You prefer a low-maintenance watch that only requires a battery change every few years. ✔️ You want a watch that’s more durable and resistant to shocks. ✔️ You are on a budget and want a reliable, cost-effective option.

Final Verdict: Which Is the Best Choice?

The choice between automatic and quartz Seiko MilSubs depends on your lifestyle and priorities. If you value tradition, craftsmanship, and a smooth movement, go for an automatic. If you need accuracy, affordability, and ease of use, a quartz MilSub is the better option.

Both types offer legendary Seiko durability and military aesthetics, making either choice a solid addition to your collection. Whether you opt for a Seiko SKX007, a Seiko SNJ025 ‘Arnie’, or another MilSub model, you can’t go wrong with a watch built for adventure!

FAQs

Q: Do Seiko MilSubs hold their value? A: Yes, particularly automatic models with classic designs and limited production runs tend to appreciate in value.

Q: Can I swim with a Seiko MilSub? A: Most Seiko MilSub watches have 200m water resistance, making them suitable for swimming and diving.

Q: Are Seiko MilSubs ISO-certified dive watches? A: Many Seiko MilSubs, like the SKX series and Prospex models, meet or exceed ISO 6425 dive watch standards.

Conclusion

Whether you choose an automatic or quartz Seiko MilSub, you’ll get a robust, military-inspired dive watch with exceptional performance. Understanding the key differences will help you pick the perfect watch for your needs.

What’s your choice—automatic or quartz? Let us know in the comments below!