5th Gear is just a bit dry. Plato, while being technically proficient just doesn't excite me about the car he's driving. Tiff hasn't really done a proper test in a while, instead doing the basic track comparisons then some chatting with either an SAS guy, or the safety features, etc.
Vicky I don't find attractive and she's not been given much to do lately, then finally Tom with the crap cars.
Top Gear has 3 people to fill in an hour, the segments are of a decent length and they get the right amount of information across. 5th Gear has 4 people to fill in 21 minutes (due to ads on 5th Gear when there are none on TG). This means the 5th Gear features are very short when they're good (like the F430 review) and the safety features take up noticably too much time. If the program was twice as long, the pedestrian safety feature of tonight's episode wouldn't have felt half as intrusive and they might have found time to do an update on the Lotus project.
Clarkson/Richard/James work really well together, they bounce jokes off each other, they're a clear team and the episodes flow well.
Tiff/Plato/Vicki/Tom are rarely seen in the same place at the same time, so you never get to know them working together and it feels like a set of individual segments with no clear flow through the program.
It's just a bit dull compared to Top Gear, IMO. Both are great shows, I get both of them every week and look forward to watching them. I just look forward to Top Gear a lot more