This is a week for sports cars and the Zeds have it all their own way.

Nissan is launching the all-new 370Z while BMW is itching to get its latest Z4 into showrooms.

Both are all-new cars: both are hot, but differ greatly in engines on offer, price and specifications. The 370Z – powered by a 3.7 - litre V6 that revs all the way to 7500 rpm - offers buyers just the one major choice, outside colours, in a well specced car: $67,990 for the six speed manual or $70,990 for the seven speed auto. This VVEL (Variable Valve Event and Lift) engine, that replaces the current 3.5- litre power plant, puts out 245 kW of power and 363 Nm of torque.  BMW are offering buyers a choice of engines.

Atop the pecking order is a twin-turbo 3.0 - litre straight six generating 225kW of power and 400 Nm of torque. BMW say it rockets to 100 km/h in just 5.1 seconds.

There is also a naturally aspirated 3.0 - litre version as well as an entry level 2.5 - litre variant to complete the range. Prices climb from $86,200 for the Z4 sDrive 23i, to $98,100 for the sDrive 30i and topped off with $116,900 for the sDrive 35i.

Nissan re-introduced the Z range in 2003, resurrecting the Z-car name that had its first life in 1969 with the launch of the much vaunted 240Z. The 370Z replaces the aging 350Z and is a full redesign of that car with a new shorter wheelbase, greater use of lightweight body materials, new engine and a new seven-speed auto with paddle shifters.

The manual also comes with the world's first synchronised down/up shift rev control. Nissan describe the 370Z as `respectful but not retro, simple yet sophisticated and unmistakably Z.”

This new Z is a chunkier car: shorter wheelbase by 100mm, shorter overall by 65 mm and wider by 30mm and the rear track by 50mm. Inside the 370Z continues the traditional two-seater sports car layout built around a deeply scooped instrument panel with a full length console separating passenger and driver's seat.

Behind the seats is an open luggage area with improved storage and accessibility and including a `shelf' that is ideal for storing briefcases. A locking glove compartment has been added.

One of the major changes to the BMW Z4 is the change from two models – roadster and coupe – to one body style featuring a retractable lightweight hardtop, giving owners the best of both worlds.

There's also a new naming structure: Z4 sDrive. The new model also gets the option of a seven-speed sports automatic transmission with double clutch for the sDrive 35i, twin turbo six. In addition there's greater cabin space, and a slightly larger bodyshell all round, including larger doors for easier entry and departure.

Like the 370Z the BMW also addresses weight issues with the bonnet, roof panels and front guards made from aluminium, as is much of the suspension. The retractable roof stows or unfolds in just 20 seconds.

Standard equipment includes leather upholstery, cruise control with brake function, park distance control, front and rear, electronic differential locking, dynamic driving control, Bi-xenon head lights, heated seats, Bluetooth, Aux in connection and USB interface.

BMW plans to have the all-new Z4 in dealerships by late this month.

Ewan Kennedy is on the road this week having his first drive of both these popular sports cars. His reports, including driving impressions, will appear soon on mister-cars.com.