OK...I'm going to preface by saying you're probably not going to find a bigger E46 lover than me so I think what I have to say will be of importance to you. E46 generation will always be my favorite because of it's design, drive, sound, and performance combination. The ZHP is the best non-M I've driven to date and I consider the best non-m BMW has ever made in terms of pure driving experience.
I contemplated for months between getting a low-mileage ZHP or the 335i. I still miss my E46 from time to time that is...until I see the F30. It's front fascia just stares at you in anger wondering why the F aren't you driving me right now? As many people have said to me, "It's a beauty and a beast".
Advantages of the E46 over the F30.
1. Hydraulic steering: Yes, the EPS does not have as much feedback as the hydraulics but it still is fantastic. You don't get as much road feel but it's super responsive, direct, stiff in sport mode and accurate. You still feel the road and the wheels turning but not as much. As others have said, once you put in higher performing tires and a lower suspension, it would feel a lot closer to the E90s and older 3ers.
2. Size/Weight: Yes, the F30 335i is a little on the heavy side being roughly 280 lbs heavier than an E46 330i. Me being a stickler about car weight can feel every pound difference. I wish it was a tad lighter but I don't mind it because I know and feel what's under the hood. The weight is still evenly distributed as always and the car does not feel that heavy. As for the size, it's definitely a pretty big mid-size sedan but you get used to it very quickly and it's not a big deal. It still drives like a sports car.
3. Suspension: Yes, the F30 has the softest sports suspension in a 3 series to date. Has little more wheel gap than normal and could be lower/stiffer. Body roll is a bit more than previous 3'ers with sports suspension. This however can easily be rectified with the H&R or the upcoming M-performance suspension. This does not mean the F30 is a "soft" car like some people think. It's still stiff and solid as hell. The chassis is 30% stiffer than the E90 and you feel it.
Those are the 3 main advantages of the E46 over the F30 but two of them will be canceled by spending a little more $.
Advantages of the F30 over the E46.
The E46 is a timeless classic design but the F30 is a modern marvel especially in M-Sport which I will always recommend to anyone thinking about which line to get. The interior and exterior is drop-dead gorgeous. The wide...low stance with the staggered tires and dual exhausts
The E46 ZHP and M3 although still make my head turn every time I see one. The interior cockpit feeling is back which was lacking in the E90. It's even more driver focused than ever. The sport seats are amazing and the ride is much smoother. The tech of course is great. The N55 engine is awesome and this is coming from a person that only loved N/A cars. N55 is the closest to N/A you can get while having that low-end torque. The sound at higher RPM is eargasmic. It roars. My car just passed 2700 miles and is just fully opening up. Every time my head hits against the headrest, it puts a smile on my face. One of my favorite things about the car is also it's efficiency. It's a 300 hp/tq beast yet I average 23 mpg when I managed 20 mpg under the same driving style in my 184 hp 2.5L E46. 36 mpg in ECO on the highway. It's a terrific daily driver yet it's got the power to burn vast majority of cars on the street.
Adding up everything the E46 has to offer vs the F30 equals out to the 335i being the "better" car at least for me. It's got a more aggressive and beautiful exterior. A better driver focused interior w/ useful Tech and more comfortable. It handles better(more body roll doesn't mean worse handling). It feels more solidly built. More advanced and powerful engine. More fuel efficient. With the enhancements like the better tires and lower suspension will make it perfect to me. The E46 is a rawer car and a little more of a driver's car than the F30 but it does not measure up to the overall package the 335i delivers.
Get the 335i in M-Sport and if you can...in 6MT for a better driving experience
^ The only day the two cars were together. I made the buyer wait till the next day just so I can have both cars together for 1 day. The first thing I'm going to get after I pay off the 335i is an E46 M3 ZCP for my weekend car