There are several trim options available. The entry-level trim package is the base Sierra 1500. When going with the base model, you can choose between either a front-wheel-drive or four-wheel-drive drivetrain. Having 4WD is a great feature to help improve handling during adverse weather conditions, if you're planning on towing gear regularly, or if you go off-roading. It will increase the price point of the Sierra and fuel economy will decline slightly, so do keep that in mind when opting for the 2WD vs 4WD.
With the base model of the Sierra, you have three engine options depending on the configuration you choose. There is the 2.7L Turbo engine, the 4.3L EcoTec3 V6, or you can go with the 5.3L EcoTec3 V8. The standard V6 does provide solid power at 285 horsepower and 305 lb-ft of torque.
If you're interested, you can upgrade your base Sierra to accept not only traditional fuel but Flex Fuel. Flex Fuel isn't as widely found at gas stations, but it is a viable option. Flex Fuel is a gasoline that is blended with ethanol. Fuels cut with ethanol are less expensive, although your fuel economy does dip as regular unleaded gives you a higher combustible liquid, which burns for longer. It can be nice to have a Flex-fuel option if you're running low on funds, but you need to fill up the tank.
One thing to consider when checking out the different trims is the safety features. The Base Sierra comes with a driver, front head, front side, passenger and rear head airbags, 4-wheel ABS and 4-wheel disc brakes, electronic stability control, daytime running lights, and traction control. However, if you want added safety features, you can find them on the next level trim packages.
The first official upgradable trim is the SLE (MSRP beginning at $39,395). With this option, there is an optional straight 6, but the two standard engines are of a different variety. Instead, you'll either want to select the larger 5.3L EcoTec3 V8 engine with an 8-speed automatic transmission (the base uses a 6-speed automatic transmission) or a 2.7L Turbo. The 2.7L Turbo offers 310 horsepower and 348 lb-ft of torque.
If you went with the 5.3L EcoTec3 V8, you'd up the engine performance to 355 horsepower and 383 lb-ft of torque; you can also spring to include the 3.0L Duramax Turbo-Diesel engine that comes with a 10-speed automatic transmission for improved fuel economy and torque. Many of the safety features are the same as the base model, although front tow hooks do come standard on the SLE. In reality, outside of a handful of minor tweaks, the biggest difference between the Sierra 1500 and the SLE trim package is the engine. The SLE also has the same entertainment features, which are AM/FM stereo, AUX input jack, MP3 player, smart device integration via Bluetooth, and WiFi hotspot (with a data plan).